Right pane tabs Jobs/Planes market + 5 new plane types with tech-spec panels + sell-plane cargo guard (ISS-047 part A)

lib/sim/movement.ts

@@ -118,3 +118,13 @@ export function requiredFuelFor(
   const rho = FUEL_DENSITY_KG_PER_L;
   return (emptyWeightKg / rho) * (Math.exp(k * rho * distanceKm) - 1);
 }
+
+// Max range from a FULL tank under the weighted model — solve requiredFuelFor(d) = maxFuel for d:
+//   (We/ρ)(e^{kρd} − 1) = F  →  d = ln(1 + ρF/We) · (We + ρF)/(ρ·burnPerKm).
+// Returns raw km (call sites round); zero fuel gives exactly 0. Pure — display-only, the sim
+// itself does not model range exhaustion (see fuelAtWeighted).
+export function maxRangeKm(burnPerKm: number, emptyWeightKg: number, maxFuel: number): number {
+  if (!(emptyWeightKg > 0)) throw new Error('emptyWeightKg must be > 0');
+  const rho = FUEL_DENSITY_KG_PER_L;
+  return Math.log(1 + (rho * maxFuel) / emptyWeightKg) * ((emptyWeightKg + rho * maxFuel) / (rho * burnPerKm));
+}