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Breguet range equation for airplanes also predates rocketry though postdates wagons. Airplanes can already have a significant portion of their weight as fuel. I

• dredmorbius 2y ago
  And by "significant", half or more their take-off weight. Boeing B-52 Stratofortress: dry weight 38.25 tonne, fuel capacity 141.6 tonne, ratio 3.7:1. Max takeoff weight: 221.3 tonne. If at max fuel, that's 63% fuel. In practice, this aircraft refuels, often multiple times, on missions, which may span the globe. Boeing 747-8: dry weight 220 tonne, fuel capacity 238.6 tonne, ratio 1.08:1. Max takeoff weight: 447.1 tonne. If at max fuel, that's 53% fuel. Much of the fuel burn is on take-off and climb, meaning that cruise portions of flight are already at significantly less than take-off weight, and further reduce with time. You'll occasionally see long-distance flight profiles in which the altitude of the aircraft increases over the flight (in 1,000 ft increments given air traffic regulations) as fuel load decreases and maximum efficient altitude increases.