diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1c3d6df..95068ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,14 @@
 # Changelog
 
+## v0.27.0 — 2026-09-20 12:27
+- **Packages now have real weight (ISS-045).** New `weight_kg REAL NOT NULL DEFAULT 2000` column on `packages` (`lib/db/schema.ts`, DDL + guarded `ALTER TABLE` migration in `lib/db/client.ts`; pre-existing rows backfill to the mid-range default). `generatePackage` draws it AFTER cargoCount: `UNIT_WEIGHT_KG[cargoType] × cargoCount × (0.7 + 0.6·rng())`, rounded to integer kg — one extra RNG draw per package, so the documented fixed draw order is now origin, dest, cargoType, cargoCount, weight jitter, [deadline window]. New tunable table `UNIT_WEIGHT_KG` in `lib/game/seed.ts` (Passengers 50 / Mail 60 / Perishables 70 / Electronics 40 / Auto parts 72 kg per passenger/pallet), chosen so every cargo type at MAX count × max jitter (1.3×) still fits the ATR alone and typical packages land ~400–2500 kg
+- **Plane capacity is now max payload kg, not 6 slots (ISS-045).** `capacity` REMOVED from `PlaneType`/`CatalogEntry`/snapshot catalog; replaced by `maxPayloadKg` — ATR 72-600 = 4800 kg (`lib/game/catalog.ts`). Server load validation (`loadPackage`, `lib/game/actions.ts`) now sums `weightKg` over the plane's loaded+expired packages and 409s with `no payload room: the ATR 72-600 carries X/Y kg` when the new package doesn't fit; expired cargo still occupies its payload. Client mirrors it: `slotsUsedFor` → `cargoWeightFor(state, planeId)` (summed kg) in `components/RightPane.tsx`, and `loadEligiblePlanes` compares used + package weight ≤ catalog maxPayloadKg so the Load button state always matches what the server accepts
+- **Payout now includes a per-kg part (ISS-045).** New `rewardFor(km, weightKg) = round(BASE_REWARD + REWARD_PER_KM·km + REWARD_PER_KG·weightKg)` with `REWARD_PER_KG = 0.5` (`lib/game/seed.ts`) — replaces the distance-only `rewardForDistanceKm`, which is deleted (no remaining callers). Typical hops stay in the ~€1–3k band
+- **Loadout display shows tonnage (ISS-045).** Left-pane fleet rows now render `X.Xt / Y.Yt` (used/max payload, one decimal) instead of `n/6 pkgs`; the on-board block filter switches to weight-based. No new endpoints — OpenAPI only gains `PackageState.weightKg` and swaps `CatalogEntry.capacity` → `maxPayloadKg`, so the e2e path list stays at twelve
+- **Test hook gains a forced weight (ISS-045).** `generatePackage` accepts an optional `weightKg` that skips the jitter RNG draw (same pattern as the v0.8.0 forced endpoints), and `POST /api/test/create-package` passes it through — so e2e flows that load several packages onto one plane stay under its payload deterministically instead of flaking on two heavy random draws (~13% would otherwise exceed 4800 kg). The hook is test-only (FLIGHT_TEST_HOOKS=1) and not part of the documented API, so the OpenAPI path list stays at twelve
+- Tests: unit — `lib/game/seed.test.ts` (reward expectations → new formula incl. per-kg part; new balance-constraint test asserting every seeded package is a positive integer kg ≤ starter maxPayloadKg; forced-weight block), `lib/game/actions.test.ts` (loadPackage fill loop now inserts weights summing past maxPayloadKg → `/no payload room/`; expired-still-occupies reworked weight-based), `components/right-pane.test.ts` (`cargoWeightFor` sums + partial-payload eligibility case; CATALOG fixture drops capacity, gains maxPayloadKg), `lib/openapi.test.ts` (exact key lists for PackageState + CatalogEntry). Type-compat only: catalog fixtures in `deriveEvents`/`mapData` tests and the e2e interfaces. E2E — `e2e/right-pane.spec.ts` asserts `maxPayloadKg === 4800`; `e2e/panes.spec.ts` loadout regex → `/^\d+\.\dt \/ \d+\.\dt$/`; snapshot key lists in `app/api/state/route.test.ts` + `e2e/state.spec.ts` gain `weightKg`; the two multi-load tests in `e2e/actions.spec.ts` pass forced weights. Fuel math untouched — the refuel-forFlight exact-liter mirrors stay as-is
+- Verified: `tsc --noEmit` clean; unit suite green locally (311, was 308); `npx playwright test --list` = 45 tests in 13 files (unchanged); e2e not run locally by design — CI verifies against an isolated stack
+
 ## v0.26.0 — 2026-09-20 11:28
 - **Flight queue UI + map rendering (ISS-043, part 2).** Builds on the part-1 backend (`PlaneState.queue`, `POST /api/planes/{id}/queue` + `/queue/cancel`, auto-chain on landing) — no new endpoints, so the OpenAPI spec and its e2e path list are untouched
 - **Dotted queue line on the map (ISS-043).** New pure builder `queuedRoutesGeoJson(planes, airportsByIcao)` in `lib/mapData.ts`: one LineString per FLYING plane with a non-empty queue, chaining `dest → queue[0] → …` — ONLY the not-yet-started legs (the active leg stays in the solid `routes-legs` layer). Reuses `greatCircleArc`, same feature/properties shape as `routesGeoJson` (`{planeId}`); arcs concatenated with the shared joint point dropped once; a plane is skipped, never guessed, when its dest or any queued ICAO is missing from the airport index. New GeoJSON source + line layer in `components/Map.tsx` — id `queue-routes`, muted slate `#64748b`, width 3, dotted via `'line-dasharray': [0.1, 1.5]` (distinct from the solid amber active leg and the `[2,2]` yellow hover dash), added after `routes-legs` but before the hover layers so a hovered trace still draws on top; pushed each poll in `applyDynamicRef` alongside the solid legs
diff --git a/app/api/packages/[id]/load/route.ts b/app/api/packages/[id]/load/route.ts
index 3597140..79e2d17 100644
--- a/app/api/packages/[id]/load/route.ts
+++ b/app/api/packages/[id]/load/route.ts
@@ -1,10 +1,11 @@
 import { loadPackage, performAction } from '@/lib/game/actions';
 
 // POST /api/packages/:id/load (v0.12.0) — body { planeId: string }. Loads an OPEN
-// package onto a GROUNDED plane at the package's origin with a free slot. 400
-// missing/non-string planeId or unknown fields; 404 unknown package/plane id; 409
-// wrong package status, plane flying, plane not at the origin, no free slots. On
-// success returns the full state snapshot (package now "loaded" on that plane).
+// package onto a GROUNDED plane at the package's origin with enough payload room
+// for its weight (v0.27.0). 400 missing/non-string planeId or unknown fields; 404
+// unknown package/plane id; 409 wrong package status, plane flying, plane not at
+// the origin, no payload room. On success returns the full state snapshot
+// (package now "loaded" on that plane).
 
 export async function POST(req: Request, ctx: { params: Promise<{ id: string }> }) {
   const { id } = await ctx.params;
diff --git a/app/api/state/route.test.ts b/app/api/state/route.test.ts
index c3e7791..9555c75 100644
--- a/app/api/state/route.test.ts
+++ b/app/api/state/route.test.ts
@@ -58,7 +58,7 @@ describe('GET /api/state', () => {
 
     const packages = body.packages as Array<Record<string, unknown>>;
     expect(packages.length).toBeGreaterThan(0);
-    for (const key of ['id', 'originIcao', 'destIcao', 'reward', 'cargoType', 'deadlineSimTime', 'status']) {
+    for (const key of ['id', 'originIcao', 'destIcao', 'reward', 'cargoType', 'weightKg', 'deadlineSimTime', 'status']) {
       expect(packages[0], `package.${key}`).toHaveProperty(key);
     }
   });
@@ -86,7 +86,7 @@ describe('GET /api/state', () => {
       expect(entry.maxFuel).toBe(type.maxFuel);
       expect(entry.burnPerKm).toBe(type.burnPerKm);
       expect(entry.speedKmh).toBe(type.speedKmh);
-      expect(entry.capacity).toBe(type.capacity); // v0.12.0 slot capacity (ATR 72-600: 6)
+      expect(entry.maxPayloadKg).toBe(type.maxPayloadKg); // v0.27.0 payload kg (ATR 72-600: 4800)
     }
 
     // Economy constants — the single source of truth stays lib/game/catalog.ts.
diff --git a/app/api/test/create-package/route.ts b/app/api/test/create-package/route.ts
index ebdf567..d8c986f 100644
--- a/app/api/test/create-package/route.ts
+++ b/app/api/test/create-package/route.ts
@@ -14,11 +14,13 @@ import { tickNow } from '@/lib/sim/engine';
 // same gate, same conventions.
 //
 // POST /api/test/create-package
-//   body { originIcao?: string, destIcao?: string, deadlineOffsetMs?: number }
+//   body { originIcao?: string, destIcao?: string, deadlineOffsetMs?: number, weightKg?: number }
 //   - ICACOs must exist in the airport dataset and differ (400 otherwise);
 //     omitted endpoints are picked at random by generatePackage.
 //   - deadlineOffsetMs defaults to a normal 6–72h game-time window (NOT the short
 //     hook deadline of expire-package) — pass an explicit value to override.
+//   - weightKg (v0.27.0) forces the package weight instead of the RNG draw, so e2e
+//     flows that load several packages can stay under the plane's payload deterministically.
 //   Returns 201 + the created package row.
 
 export async function POST(req: Request) {
@@ -38,7 +40,7 @@ export async function POST(req: Request) {
   }
   const input = body as Record<string, unknown>;
   for (const key of Object.keys(input)) {
-    if (key !== 'originIcao' && key !== 'destIcao' && key !== 'deadlineOffsetMs') {
+    if (key !== 'originIcao' && key !== 'destIcao' && key !== 'deadlineOffsetMs' && key !== 'weightKg') {
       return Response.json({ error: `unknown field "${key}"` }, { status: 400 });
     }
   }
@@ -50,6 +52,9 @@ export async function POST(req: Request) {
   if (input.deadlineOffsetMs !== undefined && (typeof input.deadlineOffsetMs !== 'number' || !Number.isFinite(input.deadlineOffsetMs))) {
     return Response.json({ error: 'deadlineOffsetMs must be a finite number' }, { status: 400 });
   }
+  if (input.weightKg !== undefined && (typeof input.weightKg !== 'number' || !Number.isFinite(input.weightKg) || input.weightKg <= 0)) {
+    return Response.json({ error: 'weightKg must be a positive finite number' }, { status: 400 });
+  }
 
   try {
     const inst = await getGameDb();
@@ -79,6 +84,7 @@ export async function POST(req: Request) {
       deadlineOffsetMs: input.deadlineOffsetMs as number | undefined,
       originIcao: input.originIcao as string | undefined,
       destIcao: input.destIcao as string | undefined,
+      weightKg: input.weightKg as number | undefined,
     });
     await inst.db.insert(schema.packages).values(created);
     await persist(inst);
diff --git a/components/LeftPane.tsx b/components/LeftPane.tsx
index 5bf48ad..8280a82 100644
--- a/components/LeftPane.tsx
+++ b/components/LeftPane.tsx
@@ -9,7 +9,7 @@ import { formatCash, formatDeadlineRelative, formatFuel, formatSimClock } from '
 import { TIME_SCALES, scaleToSlider, sliderToScale } from '@/lib/timeScale';
 import { useGameAction } from '@/lib/useGameAction';
 import { useSimClock } from '@/lib/useSimClock';
-import { slotsUsedFor } from './RightPane';
+import { cargoWeightFor } from './RightPane';
 import type { HoverTarget } from './hoverTypes';
 
 interface LeftPaneProps {
@@ -39,13 +39,12 @@ function planeLocation(p: PlaneState): string {
   return p.locationName;
 }
 
-// Cargo loadout "n/capacity pkgs" — expired packages still occupy their slot.
+// Cargo loadout "X.Xt / Y.Yt" (v0.27.0) — used/max payload in tonnes, one decimal;
+// expired packages still occupy their payload.
 function loadoutFor(state: StateSnapshot, p: PlaneState): string {
-  const used = state.packages.filter(
-    (pkg) => pkg.planeId === p.id && (pkg.status === 'loaded' || pkg.status === 'expired'),
-  ).length;
-  const capacity = state.catalog.find((e) => e.model === p.model)?.capacity ?? PLANE_TYPES[p.model]?.capacity ?? 0;
-  return `${used}/${capacity} pkgs`;
+  const used = cargoWeightFor(state, p.id);
+  const maxPayloadKg = state.catalog.find((e) => e.model === p.model)?.maxPayloadKg ?? PLANE_TYPES[p.model]?.maxPayloadKg ?? 0;
+  return `${(used / 1000).toFixed(1)}t / ${(maxPayloadKg / 1000).toFixed(1)}t`;
 }
 
 // ISS-001 — an optimistic slider value is cleared exactly when a rendered snapshot CONFIRMS it
@@ -207,7 +206,7 @@ export default function LeftPane({ state, loading, error, onRefresh, applySnapsh
   // ISS-043 (v0.26.0): a plane with queued legs always shows its block too — the queue is the
   // reason it's here even when grounded with nothing on board.
   const onboard = state
-    ? state.planes.filter((p) => p.status === 'flying' || slotsUsedFor(state, p.id) > 0 || (p.queue?.length ?? 0) > 0)
+    ? state.planes.filter((p) => p.status === 'flying' || cargoWeightFor(state, p.id) > 0 || (p.queue?.length ?? 0) > 0)
     : [];
 
   // ISS-023 (v0.21.0): Relocate — any GROUNDED plane can be repositioned to any airport via the
diff --git a/components/RightPane.tsx b/components/RightPane.tsx
index 8f0ac0b..03b32de 100644
--- a/components/RightPane.tsx
+++ b/components/RightPane.tsx
@@ -23,23 +23,25 @@ interface RightPaneProps {
 
 const planeName = (p: PlaneState): string => PLANE_TYPES[p.model]?.name ?? p.model;
 
-// Packages occupying a plane's slots — 'loaded' cargo plus 'expired' cargo, which
-// keeps its slot until it is abandoned or the plane lands at its destination.
-export function slotsUsedFor(state: StateSnapshot, planeId: string): number {
-  return state.packages.filter(
-    (p) => p.planeId === planeId && (p.status === 'loaded' || p.status === 'expired'),
-  ).length;
+// Cargo weight (kg) occupying a plane's payload — 'loaded' cargo plus 'expired'
+// cargo, which keeps its space until it is abandoned or the plane lands at its
+// destination.
+export function cargoWeightFor(state: StateSnapshot, planeId: string): number {
+  return state.packages
+    .filter((p) => p.planeId === planeId && (p.status === 'loaded' || p.status === 'expired'))
+    .reduce((sum, p) => sum + p.weightKg, 0);
 }
 
-// Planes that can load `pkg` right now: GROUNDED at the package's origin with a
-// free slot (capacity from the snapshot catalog). The Load button is enabled iff
-// this list is non-empty; exactly one entry loads directly, several show a picker.
+// Planes that can load `pkg` right now: GROUNDED at the package's origin with enough
+// payload room for it (maxPayloadKg from the snapshot catalog). The Load button is
+// enabled iff this list is non-empty; exactly one entry loads directly, several show a picker.
 export function loadEligiblePlanes(state: StateSnapshot, pkg: PackageState): PlaneState[] {
   return state.planes.filter((p) => {
     if (p.status !== 'available') return false;
     if (p.locationIcao !== pkg.originIcao) return false;
-    const capacity = state.catalog.find((e) => e.model === p.model)?.capacity ?? 0;
-    return slotsUsedFor(state, p.id) < capacity;
+    const maxPayloadKg = state.catalog.find((e) => e.model === p.model)?.maxPayloadKg ?? 0;
+    // Mirrors the server check in lib/game/actions.ts loadPackage.
+    return cargoWeightFor(state, p.id) + pkg.weightKg <= maxPayloadKg;
   });
 }
 
diff --git a/components/right-pane.test.ts b/components/right-pane.test.ts
index f08f846..4a8cc44 100644
--- a/components/right-pane.test.ts
+++ b/components/right-pane.test.ts
@@ -1,14 +1,14 @@
 import { describe, expect, it } from 'vitest';
-import { loadEligiblePlanes, slotsUsedFor } from './RightPane';
+import { cargoWeightFor, loadEligiblePlanes } from './RightPane';
 import type { PackageState, PlaneState, StateSnapshot } from '@/lib/game/state';
 
-// v0.12.0 — the package-model picker rules: a plane can LOAD a package only while
-// it is GROUNDED at the package's origin with a free slot (capacity from the
-// snapshot catalog; expired packages still occupy theirs). The Load button acts
-// directly on the single eligible plane, or shows a picker when several qualify.
+// v0.12.0 (weight model v0.27.0) — the package-model picker rules: a plane can LOAD a
+// package only while it is GROUNDED at the package's origin with enough payload room for
+// it (maxPayloadKg from the snapshot catalog; expired packages still occupy theirs). The
+// Load button acts directly on the single eligible plane, or shows a picker when several qualify.
 
 const CATALOG = [
-  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9_300, speedKmh: 510, capacity: 6 },
+  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9_300, speedKmh: 510, maxPayloadKg: 4_800 },
 ];
 
 function plane(over: Partial<PlaneState> & Pick<PlaneState, 'id'>): PlaneState {
@@ -38,6 +38,7 @@ function pkg(over: Partial<PackageState> & Pick<PackageState, 'id'>): PackageSta
     reward: 1000,
     cargoType: 'mail',
     cargoCount: 4,
+    weightKg: 1_000,
     deadlineSimTime: 1_000_000,
     status: 'open',
     planeId: null,
@@ -58,27 +59,27 @@ function snap(planes: PlaneState[], packages: PackageState[] = []): StateSnapsho
   };
 }
 
-describe('slotsUsedFor', () => {
-  it('counts loaded AND expired packages bound to the plane (both occupy a slot)', () => {
+describe('cargoWeightFor', () => {
+  it('sums the weight of loaded AND expired packages bound to the plane (both occupy payload)', () => {
     const s = snap(
       [plane({ id: 'p1' })],
       [
-        pkg({ id: 'a', status: 'loaded', planeId: 'p1' }),
-        pkg({ id: 'b', status: 'expired', planeId: 'p1' }),
-        pkg({ id: 'c', status: 'open', planeId: null }), // not on any plane
-        pkg({ id: 'd', status: 'delivered', planeId: 'p1' }), // terminal — slot long freed
+        pkg({ id: 'a', status: 'loaded', planeId: 'p1', weightKg: 800 }),
+        pkg({ id: 'b', status: 'expired', planeId: 'p1', weightKg: 500 }),
+        pkg({ id: 'c', status: 'open', planeId: null, weightKg: 9_000 }), // not on any plane
+        pkg({ id: 'd', status: 'delivered', planeId: 'p1', weightKg: 700 }), // terminal — payload long freed
       ],
     );
-    expect(slotsUsedFor(s, 'p1')).toBe(2);
+    expect(cargoWeightFor(s, 'p1')).toBe(1_300);
   });
 
   it('is 0 for a plane with no bound cargo', () => {
-    expect(slotsUsedFor(snap([plane({ id: 'p1' })]), 'p1')).toBe(0);
+    expect(cargoWeightFor(snap([plane({ id: 'p1' })]), 'p1')).toBe(0);
   });
 });
 
 describe('loadEligiblePlanes (Load button eligibility)', () => {
-  it('includes only grounded planes at the package origin with a free slot', () => {
+  it('includes only grounded planes at the package origin with enough payload room', () => {
     const s = snap([
       plane({ id: 'at-origin' }), // eligible
       plane({ id: 'elsewhere', locationIcao: 'LEMD' }), // wrong airport
@@ -87,18 +88,23 @@ describe('loadEligiblePlanes (Load button eligibility)', () => {
     expect(loadEligiblePlanes(s, pkg({ id: 'x' })).map((p) => p.id)).toEqual(['at-origin']);
   });
 
-  it('excludes a plane whose slots are full (capacity from the catalog)', () => {
-    const packages = Array.from({ length: 6 }, (_, i) =>
-      pkg({ id: `fill-${i}`, status: 'loaded', planeId: 'full' }),
+  it('a plane with partial payload can still load a package that fits', () => {
+    const s = snap([plane({ id: 'partial' })], [pkg({ id: 'onboard', status: 'loaded', planeId: 'partial', weightKg: 3_000 })]);
+    expect(loadEligiblePlanes(s, pkg({ id: 'x' })).map((p) => p.id)).toEqual(['partial']); // 3000 + 1000 ≤ 4800
+  });
+
+  it('excludes a plane whose payload is full (maxPayloadKg from the catalog)', () => {
+    const packages = Array.from({ length: 4 }, (_, i) =>
+      pkg({ id: `fill-${i}`, status: 'loaded', planeId: 'full', weightKg: 1_200 }), // 4 × 1200 = 4800
     );
     const s = snap([plane({ id: 'full' })], packages);
     expect(loadEligiblePlanes(s, pkg({ id: 'x' }))).toEqual([]);
   });
 
-  it('a full plane with one slot freed by an expired package still counts as full', () => {
+  it('a plane at its limit with an expired package still counts as full', () => {
     const packages = [
-      ...Array.from({ length: 5 }, (_, i) => pkg({ id: `fill-${i}`, status: 'loaded', planeId: 'full' })),
-      pkg({ id: 'exp', status: 'expired', planeId: 'full' }), // occupies its slot
+      ...Array.from({ length: 4 }, (_, i) => pkg({ id: `fill-${i}`, status: 'loaded', planeId: 'full', weightKg: 960 })),
+      pkg({ id: 'exp', status: 'expired', planeId: 'full', weightKg: 960 }), // occupies its payload — 5 × 960 = 4800
     ];
     const s = snap([plane({ id: 'full' })], packages);
     expect(loadEligiblePlanes(s, pkg({ id: 'x' }))).toEqual([]);
@@ -114,7 +120,7 @@ describe('loadEligiblePlanes (Load button eligibility)', () => {
     expect(loadEligiblePlanes(s, pkg({ id: 'x' }))).toEqual([]);
   });
 
-  it('a plane with an unknown model has no capacity → never eligible', () => {
+  it('a plane with an unknown model has no maxPayloadKg in the catalog → never eligible', () => {
     const s = snap([plane({ id: 'mystery', model: 'mystery' })]);
     expect(loadEligiblePlanes(s, pkg({ id: 'x' }))).toEqual([]);
   });
diff --git a/e2e/actions.spec.ts b/e2e/actions.spec.ts
index 60dd141..e416d25 100644
--- a/e2e/actions.spec.ts
+++ b/e2e/actions.spec.ts
@@ -53,8 +53,16 @@ async function getState(page: Page): Promise<StateBody> {
 }
 
 // The e2e instance runs with FLIGHT_TEST_HOOKS=1 (docker-compose.yml) — the hook is live.
-async function createPackage(page: Page, from?: string, to?: string, deadlineOffsetMs?: number): Promise<StateBody['packages'][number]> {
-  const res = await page.request.post('/api/test/create-package', { data: { originIcao: from, destIcao: to, deadlineOffsetMs } });
+// weightKg (v0.27.0) forces the package weight instead of the RNG draw, so flows that load
+// several packages onto one plane stay under its payload deterministically.
+async function createPackage(
+  page: Page,
+  from?: string,
+  to?: string,
+  deadlineOffsetMs?: number,
+  weightKg?: number,
+): Promise<StateBody['packages'][number]> {
+  const res = await page.request.post('/api/test/create-package', { data: { originIcao: from, destIcao: to, deadlineOffsetMs, weightKg } });
   expect(res.status()).toBe(201);
   return (await res.json()) as StateBody['packages'][number];
 }
@@ -240,9 +248,10 @@ test('abandon while grounded deducts exactly the formula penalty', async ({ page
   await flyHomeViaApi(page);
   const before = await getState(page);
 
-  // Two packages at the hub — load both, abandon one through the UI.
-  const pkgA = await createPackage(page, HUB, 'LEMD', 24 * 3_600_000);
-  const pkgB = await createPackage(page, HUB, 'LEMD', 24 * 3_600_000);
+  // Two packages at the hub — load both, abandon one through the UI. Forced weights keep
+  // the pair under the starter's payload (v0.27.0) so both loads are deterministic.
+  const pkgA = await createPackage(page, HUB, 'LEMD', 24 * 3_600_000, 1_000);
+  const pkgB = await createPackage(page, HUB, 'LEMD', 24 * 3_600_000, 1_000);
   for (const p of [pkgA, pkgB]) {
     const res = await page.request.post(`/api/packages/${p.id}/load`, { data: { planeId: 'plane-starter' } });
     expect(res.ok()).toBeTruthy();
@@ -282,8 +291,8 @@ test('expired packages deliver and abandon with no reward and no penalty', async
   // destination differs from A's so it stays bound on the plane at LEMD arrival and can
   // still be abandoned (an expired package whose dest matches the arrival airport is
   // unbound by the tick instead).
-  const pkgA = await createPackage(page, HUB, 'LEMD', 10_000); // short game-time deadline
-  const pkgB = await createPackage(page, HUB, 'EHAM', 10_000);
+  const pkgA = await createPackage(page, HUB, 'LEMD', 10_000, 1_000); // short game-time deadline; forced weights keep the pair under payload (v0.27.0)
+  const pkgB = await createPackage(page, HUB, 'EHAM', 10_000, 1_000);
   for (const p of [pkgA, pkgB]) {
     const res = await page.request.post(`/api/packages/${p.id}/load`, { data: { planeId: 'plane-starter' } });
     expect(res.ok()).toBeTruthy();
diff --git a/e2e/panes.spec.ts b/e2e/panes.spec.ts
index efe108a..b003b2c 100644
--- a/e2e/panes.spec.ts
+++ b/e2e/panes.spec.ts
@@ -62,10 +62,10 @@ test('left pane renders wallet, reputation and the starter fleet at Frankfurt',
     await expect(row).toContainText(truth.locationName);
   }
 
-  // v0.12.0 loadout: "n/capacity pkgs" (capacity from the snapshot catalog — ATR 72-600 = 6).
+  // v0.27.0 loadout: "X.Xt / Y.Yt" tonnage (used/max payload from the snapshot catalog — ATR 72-600 = 4.8t).
   const loadout = page.getByTestId('plane-loadout-plane-starter');
   await expect(loadout).toBeVisible();
-  expect((await loadout.textContent()) ?? '').toMatch(/^\d+\/6 pkgs$/);
+  expect((await loadout.textContent()) ?? '').toMatch(/^\d+\.\dt \/ \d+\.\dt$/);
 
   // Sim clock renders (UTC wall-clock of the game time).
   await expect(page.getByTestId('sim-clock')).toContainText(/UTC/);
diff --git a/e2e/right-pane.spec.ts b/e2e/right-pane.spec.ts
index bce694c..2df7688 100644
--- a/e2e/right-pane.spec.ts
+++ b/e2e/right-pane.spec.ts
@@ -42,7 +42,7 @@ interface CatalogEntry {
   burnPerKm: number;
   emptyWeightKg: number; // v0.16.0 weighted burn input
   speedKmh: number;
-  capacity: number;
+  maxPayloadKg: number; // v0.27.0 — replaces the v0.12.0 slot capacity
 }
 
 interface StateBody {
@@ -309,7 +309,7 @@ test('market buy/sell render with previews from the catalog in /api/state; left-
   const body = await getState(page); // authoritative catalog + economy constants (v0.10.0)
   expect(body.catalog.length).toBeGreaterThan(0);
   const entry = body.catalog.find((e) => e.model === 'atr72')!;
-  expect(entry.capacity).toBe(6); // v0.12.0 slot capacity exposed in the snapshot
+  expect(entry.maxPayloadKg).toBe(4_800); // ATR 72-600 max payload (lib/game/catalog.ts)
 
   await page.goto('/');
   // Buy: the model picker lists the catalog entry and the price preview is its full price.
diff --git a/e2e/state.spec.ts b/e2e/state.spec.ts
index bfb9f6b..a236897 100644
--- a/e2e/state.spec.ts
+++ b/e2e/state.spec.ts
@@ -36,7 +36,7 @@ test('GET /api/state returns a seeded snapshot', async ({ page }) => {
 
   expect(Array.isArray(body.packages)).toBe(true);
   expect(body.packages.length).toBeGreaterThan(0);
-  for (const key of ['id', 'originIcao', 'destIcao', 'reward', 'cargoType', 'deadlineSimTime', 'status']) {
+  for (const key of ['id', 'originIcao', 'destIcao', 'reward', 'cargoType', 'weightKg', 'deadlineSimTime', 'status']) {
     expect(body.packages[0], `package.${key}`).toHaveProperty(key);
   }
 });
diff --git a/lib/db/client.ts b/lib/db/client.ts
index 3d179a3..cb9ff97 100644
--- a/lib/db/client.ts
+++ b/lib/db/client.ts
@@ -40,6 +40,7 @@ CREATE TABLE IF NOT EXISTS packages (
   reward REAL NOT NULL,
   cargo_type TEXT NOT NULL,
   cargo_count INTEGER NOT NULL,
+  weight_kg REAL NOT NULL DEFAULT 2000,
   deadline_sim_time INTEGER NOT NULL,
   status TEXT NOT NULL,
   plane_id TEXT,
@@ -77,6 +78,10 @@ function migrateColumns(raw: RawSqlJsDatabase): void {
   if (!cols('planes').has('queue')) {
     raw.exec(`ALTER TABLE planes ADD COLUMN queue TEXT NOT NULL DEFAULT '[]'`);
   }
+  // v0.27.0 (ISS-045): package weight — pre-existing rows backfill to a mid-range default.
+  if (!cols('packages').has('weight_kg')) {
+    raw.exec('ALTER TABLE packages ADD COLUMN weight_kg REAL NOT NULL DEFAULT 2000');
+  }
 }
 
 // v0.12.0 one-time migration: contracts world → packages world. Detected by the
diff --git a/lib/db/schema.ts b/lib/db/schema.ts
index 4ea1a20..b5aa7cd 100644
--- a/lib/db/schema.ts
+++ b/lib/db/schema.ts
@@ -37,6 +37,9 @@ export const packages = sqliteTable('packages', {
   reward: real('reward').notNull(),
   cargoType: text('cargo_type').notNull(),
   cargoCount: integer('cargo_count').notNull(),
+  // Package weight in kg (v0.27.0, ISS-045) — drives load validation (plane payload)
+  // and the per-kg part of the payout. Pre-existing rows backfill to the default.
+  weightKg: real('weight_kg').notNull().default(2000),
   deadlineSimTime: integer('deadline_sim_time').notNull(),
   // 'expired' = an open OR loaded package whose deadline passed on a tick. Loaded
   // expired packages keep occupying their slot, deliver no reward, and abandon free.
diff --git a/lib/deriveEvents.test.ts b/lib/deriveEvents.test.ts
index 8d52892..f7ef9ac 100644
--- a/lib/deriveEvents.test.ts
+++ b/lib/deriveEvents.test.ts
@@ -6,7 +6,7 @@ import { diffSnapshots } from './deriveEvents';
 // feature, unit-tested in node like advanceSimClock/fetchState.
 
 const CATALOG = [
-  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9300, speedKmh: 510, capacity: 6 },
+  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9300, speedKmh: 510, maxPayloadKg: 4800 },
 ];
 
 const basePlane = (id: string): PlaneState => ({
@@ -34,6 +34,7 @@ const basePackage = (id: string): PackageState => ({
   reward: 1234.5,
   cargoType: 'mail',
   cargoCount: 2,
+  weightKg: 600,
   deadlineSimTime: 0,
   status: 'open',
   planeId: null,
diff --git a/lib/game/actions.test.ts b/lib/game/actions.test.ts
index 140e43c..d682787 100644
--- a/lib/game/actions.test.ts
+++ b/lib/game/actions.test.ts
@@ -127,27 +127,27 @@ describe('loadPackage', () => {
     await expectActionError(loadPackage(inst, 'p-open', 'plane-starter'), 409, /at LEMD/);
   });
 
-  it('rejects loading when the plane has no free slot (capacity from catalog)', async () => {
+  it('rejects loading when the plane has no payload room (maxPayloadKg from catalog)', async () => {
     const inst = await freshDb('load-full.db');
-    await insertOpenPackage(inst, 'p-new');
-    // Fill all atr72 slots with loaded cargo…
-    for (let i = 0; i < PLANE_TYPES.atr72.capacity; i++) {
-      await insertOpenPackage(inst, `p-fill-${i}`, { status: 'loaded', planeId: 'plane-starter' });
+    await insertOpenPackage(inst, 'p-new', { weightKg: 1_000 });
+    // Fill past maxPayloadKg with loaded cargo…
+    const chunk = Math.floor(PLANE_TYPES.atr72.maxPayloadKg / 3) + 1; // 3 chunks > max
+    for (let i = 0; i < 3; i++) {
+      await insertOpenPackage(inst, `p-fill-${i}`, { status: 'loaded', planeId: 'plane-starter', weightKg: chunk });
     }
 
-    await expectActionError(loadPackage(inst, 'p-new', 'plane-starter'), 409, /no free slots/i);
+    await expectActionError(loadPackage(inst, 'p-new', 'plane-starter'), 409, /no payload room/i);
   });
 
-  it('counts expired packages as occupying their slot too', async () => {
+  it('counts expired packages as occupying their payload too', async () => {
     const inst = await freshDb('load-expiredslot.db');
-    await insertOpenPackage(inst, 'p-new');
-    // capacity − 1 loaded + 1 expired = full.
-    for (let i = 0; i < PLANE_TYPES.atr72.capacity - 1; i++) {
-      await insertOpenPackage(inst, `p-fill-${i}`, { status: 'loaded', planeId: 'plane-starter' });
-    }
-    await insertOpenPackage(inst, 'p-expired-slot', { status: 'expired', planeId: 'plane-starter' });
+    await insertOpenPackage(inst, 'p-new', { weightKg: 1_000 });
+    // Half + half (expired) leaves no room — each alone would fit.
+    const half = Math.floor(PLANE_TYPES.atr72.maxPayloadKg / 2) + 1;
+    await insertOpenPackage(inst, 'p-loaded-half', { status: 'loaded', planeId: 'plane-starter', weightKg: half });
+    await insertOpenPackage(inst, 'p-expired-slot', { status: 'expired', planeId: 'plane-starter', weightKg: half });
 
-    await expectActionError(loadPackage(inst, 'p-new', 'plane-starter'), 409, /no free slots/i);
+    await expectActionError(loadPackage(inst, 'p-new', 'plane-starter'), 409, /no payload room/i);
   });
 });
 
diff --git a/lib/game/actions.ts b/lib/game/actions.ts
index 8744644..08c711e 100644
--- a/lib/game/actions.ts
+++ b/lib/game/actions.ts
@@ -20,7 +20,7 @@ import { HUB_ICAO } from './seed';
 // GameActionError carrying the HTTP status:
 //   404 — unknown entity id
 //   409 — valid ids but the current state forbids the action (wrong package/plane
-//         status, plane not at origin, no free slot, insufficient fuel/funds, last plane)
+//         status, plane not at origin, no payload room, insufficient fuel/funds, last plane)
 //   400 — bad input that isn't an existence problem (unknown airport/model)
 
 export class GameActionError extends Error {
@@ -43,8 +43,9 @@ async function airportByIcao(icao: string): Promise<{ icao: string; lat: number;
 // --- Load (POST /api/packages/:id/load {planeId}) ---
 
 // open → loaded, bound to the plane. The plane must be GROUNDED at the package's
-// origin with a free slot (slots = packages 'loaded' or 'expired' on it — expired
-// cargo keeps occupying its space until delivered/abandoned).
+// origin with enough payload room (v0.27.0: used kg = sum of weightKg over packages
+// 'loaded' or 'expired' on it — expired cargo keeps occupying its space until
+// delivered/abandoned).
 export async function loadPackage(inst: GameDb, packageId: string, planeId: string): Promise<void> {
   const [pkgRows, planeRows] = await Promise.all([
     inst.db.select().from(schema.packages).where(eq(schema.packages.id, packageId)),
@@ -69,13 +70,12 @@ export async function loadPackage(inst: GameDb, packageId: string, planeId: stri
 
   const type = PLANE_TYPES[plane.model];
   if (!type) throw new Error(`unknown plane model ${plane.model}`); // → 500, cannot happen for seeded data
-  const occupied = (
-    await inst.db.select().from(schema.packages).where(
-      and(inArray(schema.packages.status, ['loaded', 'expired']), eq(schema.packages.planeId, plane.id)),
-    )
-  ).length;
-  if (occupied >= type.capacity) {
-    throw new GameActionError(409, `no free slots: the ${type.name} carries ${occupied}/${type.capacity} packages`);
+  const occupied = await inst.db.select({ weightKg: schema.packages.weightKg }).from(schema.packages).where(
+    and(inArray(schema.packages.status, ['loaded', 'expired']), eq(schema.packages.planeId, plane.id)),
+  );
+  const usedKg = occupied.reduce((sum, r) => sum + (r.weightKg ?? 0), 0);
+  if (usedKg + pkg.weightKg > type.maxPayloadKg) {
+    throw new GameActionError(409, `no payload room: the ${type.name} carries ${Math.round(usedKg)}/${type.maxPayloadKg} kg`);
   }
 
   await inst.db.update(schema.packages)
diff --git a/lib/game/catalog.ts b/lib/game/catalog.ts
index c644963..26bc27e 100644
--- a/lib/game/catalog.ts
+++ b/lib/game/catalog.ts
@@ -16,8 +16,10 @@ export interface PlaneType {
   // Market price in € (v0.8.0): buying costs `price`, selling pays out
   // SELL_FRACTION × price.
   price: number;
-  // Cargo slot capacity (v0.12.0): how many packages can be loaded on one plane.
-  capacity: number;
+  // Max payload in kg (v0.27.0, ISS-045 — replaces the v0.12.0 slot count): total
+  // package weight that can be loaded on one plane. ATR 72-600-class figure, tuned
+  // so every cargo type at max count × 1.3 jitter still fits alone (see UNIT_WEIGHT_KG).
+  maxPayloadKg: number;
 }
 
 export const PLANE_TYPES: Record<string, PlaneType> = {
@@ -31,7 +33,9 @@ export const PLANE_TYPES: Record<string, PlaneType> = {
     // €200k — with the starting cash of €20k and typical hop rewards (~€1–3k),
     // a second ATR takes sustained play to afford, as intended for the MVP sink.
     price: 200_000,
-    capacity: 6,
+    // ponytail: balance-tunable payload (kg) — every cargo type at max count × 1.3 jitter
+    // must stay below this so any single package fits alone; typical loads carry ~3–6 packages.
+    maxPayloadKg: 4_800,
   },
 };
 
@@ -57,7 +61,8 @@ export interface CatalogEntry {
   // lib/sim/movement.ts with these + FUEL_DENSITY_KG_PER_L.
   emptyWeightKg: number;
   speedKmh: number;
-  capacity: number;
+  // Max payload in kg (v0.27.0) — total package weight that can be loaded on one plane.
+  maxPayloadKg: number;
 }
 
 // The catalog as a flat array, one entry per plane type — the single source of
@@ -71,6 +76,6 @@ export function catalogEntries(): CatalogEntry[] {
     burnPerKm: t.burnPerKm,
     emptyWeightKg: t.emptyWeightKg,
     speedKmh: t.speedKmh,
-    capacity: t.capacity,
+    maxPayloadKg: t.maxPayloadKg,
   }));
 }
diff --git a/lib/game/seed.test.ts b/lib/game/seed.test.ts
index 4d5ddfb..de8d109 100644
--- a/lib/game/seed.test.ts
+++ b/lib/game/seed.test.ts
@@ -9,8 +9,9 @@ import {
   generatePackage,
   HUB_ICAO,
   mulberry32,
+  REWARD_PER_KG,
   REWARD_PER_KM,
-  rewardForDistanceKm,
+  rewardFor,
   STARTING_CASH,
   STARTING_REPUTATION,
   type SeedAirport,
@@ -70,12 +71,26 @@ describe('buildSeed', () => {
     expect(new Set(seed.packages.map((c) => c.id)).size).toBe(seed.packages.length);
   });
 
-  it('scales reward by haversine distance: round(500 + 2.5 * km)', () => {
+  it('applies the reward formula: round(500 + 2.5 * km + 0.5 * weightKg)', () => {
     const seed = seedWith(42);
     for (const c of seed.packages) {
       const o = AIRPORTS.find((a) => a.icao === c.originIcao)!;
       const d = AIRPORTS.find((a) => a.icao === c.destIcao)!;
-      expect(c.reward).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon)));
+      expect(c.reward).toBe(
+        Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon) + REWARD_PER_KG * c.weightKg),
+      );
+    }
+  });
+
+  it('gives every package a positive integer weight that fits the starter plane alone (balance constraint)', () => {
+    const maxPayload = PLANE_TYPES[STARTER_MODEL].maxPayloadKg;
+    for (const seed of [seedWith(42), seedWith(7)]) {
+      for (const c of seed.packages) {
+        expect(Number.isInteger(c.weightKg)).toBe(true);
+        expect(c.weightKg).toBeGreaterThan(0);
+        // max count × max jitter (1.3×) must still fit the ATR alone — see UNIT_WEIGHT_KG.
+        expect(c.weightKg).toBeLessThanOrEqual(maxPayload);
+      }
     }
   });
 
@@ -106,9 +121,9 @@ describe('buildSeed', () => {
     expect(() => buildSeed({ airports: AIRPORTS.slice(0, 1), rng: mulberry32(42), nowMs: NOW })).toThrow();
   });
 
-  it('rewardForDistanceKm applies the documented formula', () => {
-    expect(rewardForDistanceKm(0)).toBe(BASE_REWARD);
-    expect(rewardForDistanceKm(1000)).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * 1000));
+  it('rewardFor applies the documented formula', () => {
+    expect(rewardFor(0, 0)).toBe(BASE_REWARD);
+    expect(rewardFor(1000, 2_000)).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * 1000 + REWARD_PER_KG * 2_000));
   });
 });
 
@@ -127,7 +142,9 @@ describe('generatePackage (shared seed/spawn builder)', () => {
 
     const o = AIRPORTS.find((a) => a.icao === c.originIcao)!;
     const d = AIRPORTS.find((a) => a.icao === c.destIcao)!;
-    expect(c.reward).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon)));
+    expect(c.reward).toBe(
+      Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon) + REWARD_PER_KG * c.weightKg),
+    );
 
     // Same 6–72h game-time deadline window as the seed.
     expect(c.deadlineSimTime).toBeGreaterThan(NOW + 6 * 3_600_000 - 1);
@@ -173,7 +190,9 @@ describe('generatePackage (shared seed/spawn builder)', () => {
 
       const o = AIRPORTS.find((a) => a.icao === c.originIcao)!;
       const d = AIRPORTS.find((a) => a.icao === c.destIcao)!;
-      expect(c.reward).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon)));
+      expect(c.reward).toBe(
+        Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon) + REWARD_PER_KG * c.weightKg),
+      );
     });
 
     it('destIcao forces the destination; origin stays random but distinct', () => {
@@ -189,7 +208,9 @@ describe('generatePackage (shared seed/spawn builder)', () => {
 
       const o = AIRPORTS[0]; // EDDF
       const d = AIRPORTS[1]; // EHAM
-      expect(c.reward).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon)));
+      expect(c.reward).toBe(
+        Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon) + REWARD_PER_KG * c.weightKg),
+      );
     });
 
     it('is deterministic for a fixed RNG with forced endpoints', () => {
@@ -212,4 +233,22 @@ describe('generatePackage (shared seed/spawn builder)', () => {
       expect(a).toEqual(b);
     });
   });
+
+  describe('forced weight (v0.27.0 e2e hook)', () => {
+    it('weightKg forces the package weight and feeds the payout', () => {
+      const c = generatePackage({ id: 'c-w', airports: AIRPORTS, rng: mulberry32(42), nowMs: NOW, weightKg: 1_234 });
+      expect(c.weightKg).toBe(1_234);
+
+      const o = AIRPORTS.find((a) => a.icao === c.originIcao)!;
+      const d = AIRPORTS.find((a) => a.icao === c.destIcao)!;
+      expect(c.reward).toBe(Math.round(BASE_REWARD + REWARD_PER_KM * haversineKm(o.lat, o.lon, d.lat, d.lon) + REWARD_PER_KG * 1_234));
+
+      // Deterministic for a fixed RNG…
+      const again = generatePackage({ id: 'c-w', airports: AIRPORTS, rng: mulberry32(42), nowMs: NOW, weightKg: 1_234 });
+      expect(again).toEqual(c);
+      // …and the forced value consumes no RNG draw — the deadline lands where an unforced call's jitter would.
+      const unforced = generatePackage({ id: 'c-u', airports: AIRPORTS, rng: mulberry32(42), nowMs: NOW });
+      expect(c.deadlineSimTime).not.toBe(unforced.deadlineSimTime);
+    });
+  });
 });
diff --git a/lib/game/seed.ts b/lib/game/seed.ts
index cef39a5..1038556 100644
--- a/lib/game/seed.ts
+++ b/lib/game/seed.ts
@@ -50,6 +50,8 @@ export interface SeedPackage {
   reward: number;
   cargoType: string;
   cargoCount: number;
+  // Package weight in kg (v0.27.0, ISS-045) — unit weight × count with ±30% jitter.
+  weightKg: number;
   deadlineSimTime: number;
   status: 'open';
   planeId: null;
@@ -80,10 +82,12 @@ export const PACKAGE_COUNT_MAX = 12; // inclusive
 // count after expiries, so the job board never runs dry.
 export const MARKET_TARGET_OPEN_PACKAGES = 10;
 
-// Reward formula (v0.6.0 — deliberately simple; real revenue/cost modeling is a
-// later increment): reward = BASE_REWARD + REWARD_PER_KM * great-circle km.
+// Reward formula (v0.6.0 distance part, deliberately simple; real revenue/cost
+// modeling is a later increment; v0.27.0 weight part): reward = BASE_REWARD +
+// REWARD_PER_KM * great-circle km + REWARD_PER_KG * package weight kg.
 export const BASE_REWARD = 500;
 export const REWARD_PER_KM = 2.5;
+export const REWARD_PER_KG = 0.5;
 
 // Package deadlines: now + a plausible game-time window of 6–72 hours.
 const DEADLINE_MIN_HOURS = 6;
@@ -91,19 +95,33 @@ const DEADLINE_MAX_HOURS = 72;
 
 const CARGO_TYPES = ['Passengers', 'Mail', 'Perishables', 'Electronics', 'Auto parts'] as const;
 
-export function rewardForDistanceKm(km: number): number {
-  return Math.round(BASE_REWARD + REWARD_PER_KM * km);
+// ponytail: balance-tunable unit weights (kg per passenger/pallet). Chosen so every cargo
+// type at MAX count × max jitter (1.3×) still fits the ATR 72-600's payload alone, and
+// typical packages land ~400–2500 kg — a normal flight carries roughly 3–6 by weight.
+export const UNIT_WEIGHT_KG: Record<string, number> = {
+  Passengers: 50, // max 50 × 68 × 1.3 = 4420 < 4800
+  Mail: 60, // max 60 × 50 × 1.3 = 3900
+  Perishables: 70, // max 70 × 50 × 1.3 = 4550
+  Electronics: 40, // max 40 × 50 × 1.3 = 2600
+  'Auto parts': 72, // max 72 × 50 × 1.3 = 4680
+};
+
+export function rewardFor(km: number, weightKg: number): number {
+  return Math.round(BASE_REWARD + REWARD_PER_KM * km + REWARD_PER_KG * weightKg);
 }
 
 // Shared package generator, used by BOTH the first-run seed and the runtime
 // market spawn (v0.7.0) so spawned packages match seeded ones exactly: random
-// distinct airports from the dataset, distance-based reward, cargo flavor,
-// deadline now + 6–72h game time (or now + deadlineOffsetMs when given — used by
-// the e2e test hook to force a near-term expiry). The RNG call order per package
-// is fixed: origin, dest, cargoType, cargoCount, [deadline window].
+// distinct airports from the dataset, distance+weight-based reward, cargo flavor,
+// weight = unit weight × count with ±30% jitter (v0.27.0), deadline now + 6–72h
+// game time (or now + deadlineOffsetMs when given — used by the e2e test hook to
+// force a near-term expiry). The RNG call order per package is fixed: origin,
+// dest, cargoType, cargoCount, weight jitter, [deadline window].
 // v0.8.0: originIcao/destIcao optionally FORCE an endpoint (spawn coverage rule +
 // the e2e create-package hook); a forced endpoint consumes no RNG draws, so
 // callers that omit both get byte-identical behavior to before.
+// v0.27.0: weightKg optionally FORCES the package weight (e2e hook) — it skips the
+// jitter draw, same pattern as forced endpoints.
 export function generatePackage(input: {
   id: string;
   airports: SeedAirport[];
@@ -112,6 +130,7 @@ export function generatePackage(input: {
   deadlineOffsetMs?: number;
   originIcao?: string;
   destIcao?: string;
+  weightKg?: number;
 }): SeedPackage {
   const { airports, rng, nowMs } = input;
   if (airports.length < 2) throw new Error('package generation needs at least two airports');
@@ -143,6 +162,9 @@ export function generatePackage(input: {
   // Passengers up to the ATR 72's ~68 seats; other cargo in pallets.
   const cargoCount =
     cargoType === 'Passengers' ? 1 + Math.floor(rng() * 68) : 1 + Math.floor(rng() * 50);
+  // Weight (v0.27.0): unit weight × count with ±30% jitter, integer kg — drawn AFTER
+  // cargoCount so the fixed RNG order above holds; a forced weightKg skips the draw.
+  const weightKg = input.weightKg ?? Math.round(UNIT_WEIGHT_KG[cargoType] * cargoCount * (0.7 + 0.6 * rng()));
   const deadlineMs =
     input.deadlineOffsetMs ?? (DEADLINE_MIN_HOURS + rng() * (DEADLINE_MAX_HOURS - DEADLINE_MIN_HOURS)) * 3_600_000;
 
@@ -150,9 +172,10 @@ export function generatePackage(input: {
     id: input.id,
     originIcao: origin.icao,
     destIcao: dest.icao,
-    reward: rewardForDistanceKm(km),
+    reward: rewardFor(km, weightKg),
     cargoType,
     cargoCount,
+    weightKg,
     deadlineSimTime: Math.round(nowMs + deadlineMs),
     status: 'open',
     planeId: null,
diff --git a/lib/game/state.ts b/lib/game/state.ts
index 0218db6..ae2a185 100644
--- a/lib/game/state.ts
+++ b/lib/game/state.ts
@@ -50,6 +50,8 @@ export interface PackageState {
   reward: number;
   cargoType: string;
   cargoCount: number;
+  // Package weight in kg (v0.27.0, ISS-045) — drives load validation + per-kg payout.
+  weightKg: number;
   deadlineSimTime: number;
   status: 'open' | 'loaded' | 'delivered' | 'expired' | 'abandoned';
   planeId: string | null;
@@ -135,6 +137,7 @@ export async function getStateSnapshot(): Promise<StateSnapshot> {
       reward: p.reward,
       cargoType: p.cargoType,
       cargoCount: p.cargoCount,
+      weightKg: p.weightKg,
       deadlineSimTime: p.deadlineSimTime,
       status: p.status,
       planeId: p.planeId,
diff --git a/lib/mapData.test.ts b/lib/mapData.test.ts
index eac448e..3e8e58f 100644
--- a/lib/mapData.test.ts
+++ b/lib/mapData.test.ts
@@ -17,7 +17,7 @@ function snapshot(overrides: Partial<StateSnapshot> = {}): StateSnapshot {
     planes: [],
     packages: [],
     catalog: [
-      { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9_300, speedKmh: 510, capacity: 6 },
+      { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9_300, speedKmh: 510, maxPayloadKg: 4_800 },
     ],
     fuelPricePerL: 0.8,
     sellFraction: 0.5,
diff --git a/lib/openapi.test.ts b/lib/openapi.test.ts
index 2167f66..3651a62 100644
--- a/lib/openapi.test.ts
+++ b/lib/openapi.test.ts
@@ -94,18 +94,17 @@ describe('OpenAPI spec', () => {
     const catalog = openApiSpec.components.schemas.CatalogEntry.properties;
     expect(Object.keys(catalog).sort()).toEqual([
       'burnPerKm',
-      'capacity',
       'emptyWeightKg', // v0.16.0 weighted burn model input
       'label',
       'maxFuel',
+      'maxPayloadKg', // v0.27.0 (ISS-045) — replaces the v0.12.0 slot capacity
       'model',
       'price',
       'speedKmh',
     ]);
-    for (const key of ['burnPerKm', 'emptyWeightKg', 'maxFuel', 'price', 'speedKmh'] as const) {
+    for (const key of ['burnPerKm', 'emptyWeightKg', 'maxFuel', 'maxPayloadKg', 'price', 'speedKmh'] as const) {
       expect(catalog[key].type, `CatalogEntry.${key}`).toBe('number');
     }
-    expect(catalog.capacity.type).toBe('integer'); // v0.12.0 slot capacity
     expect(catalog.model.type).toBe('string');
     expect(catalog.label.type).toBe('string');
 
@@ -140,6 +139,7 @@ describe('OpenAPI spec', () => {
       'planeId',
       'reward',
       'status',
+      'weightKg', // v0.27.0 (ISS-045) — package weight in kg
     ]);
 
     const sim = openApiSpec.components.schemas.SimState.properties;
diff --git a/lib/openapi.ts b/lib/openapi.ts
index 71a63ae..29e044a 100644
--- a/lib/openapi.ts
+++ b/lib/openapi.ts
@@ -106,7 +106,7 @@ export const openApiSpec = {
       post: {
         summary: 'Load a package onto a plane',
         description:
-          'Bind an OPEN package to a GROUNDED ("available") plane at the package\'s origin (v0.12.0). The plane needs a free slot — capacity per catalog model; expired packages still occupy theirs. The sim clock is ticked first, so the returned snapshot reflects current game time.',
+          'Bind an OPEN package to a GROUNDED ("available") plane at the package\'s origin (v0.12.0). The plane needs enough payload room for the package weight — maxPayloadKg per catalog model; expired packages still occupy theirs (v0.27.0). The sim clock is ticked first, so the returned snapshot reflects current game time.',
         operationId: 'loadPackage',
         parameters: [
           { name: 'id', in: 'path', required: true, schema: { type: 'string' } },
@@ -461,9 +461,9 @@ export const openApiSpec = {
           burnPerKm: { type: 'number', description: 'Cruise fuel burn at a full tank, liters/km (v0.16.0 weighted model calibrates to this).' },
           emptyWeightKg: { type: 'number', description: 'Operating empty weight, kg — with burnPerKm and maxFuel it drives the v0.16.0 weight-proportional burn model.' },
           speedKmh: { type: 'number', description: 'Cruise speed, km/h.' },
-          capacity: { type: 'integer', description: 'Cargo slot capacity — packages that can be loaded on one plane (v0.12.0).' },
+          maxPayloadKg: { type: 'number', description: 'Max payload in kg — total package weight that can be loaded on one plane (v0.27.0, replaces the v0.12.0 slot count).' },
         },
-        required: ['model', 'label', 'price', 'maxFuel', 'burnPerKm', 'emptyWeightKg', 'speedKmh', 'capacity'],
+        required: ['model', 'label', 'price', 'maxFuel', 'burnPerKm', 'emptyWeightKg', 'speedKmh', 'maxPayloadKg'],
       },
       AccountState: {
         type: 'object',
@@ -498,7 +498,7 @@ export const openApiSpec = {
       LoadPackageRequest: {
         type: 'object',
         properties: {
-          planeId: { type: 'string', description: 'A GROUNDED ("available") plane at the package\'s origin with a free slot.' },
+          planeId: { type: 'string', description: 'A GROUNDED ("available") plane at the package\'s origin with enough payload room for it (v0.27.0).' },
         },
         required: ['planeId'],
       },
@@ -618,6 +618,7 @@ export const openApiSpec = {
           reward: { type: 'number' },
           cargoType: { type: 'string' },
           cargoCount: { type: 'integer' },
+          weightKg: { type: 'number', description: 'Package weight in kg (v0.27.0) — drives load validation and the per-kg payout part.' },
           deadlineSimTime: { type: 'integer', description: 'Sim-clock epoch ms (game time)' },
           // 'expired' = an open OR loaded package whose deadline passed on a tick;
           // loaded expired packages keep their slot, deliver no reward, abandon free.
@@ -634,6 +635,7 @@ export const openApiSpec = {
           'reward',
           'cargoType',
           'cargoCount',
+          'weightKg', // v0.27.0 (ISS-045) — package weight in kg
           'deadlineSimTime',
           'status',
           'planeId',
diff --git a/package.json b/package.json
index 3618029..8954ca2 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "flight-ops",
-  "version": "0.26.0",
+  "version": "0.27.0",
   "private": true,
   "scripts": {
     "dev": "next dev -p 3000",