What is the highest a jet airplane can fly?
The highest flying jet aircraft is most likely the SR-71 “Blackbird” which could fly at an altitude of at least 85,000 feet in sustained flight. However, there is speculation that the SR-71 could fly higher (maybe as high as 100,000 feet), but the details remain classified. Several other aircraft have flown higher using a “zoom” technique. In a zoom climb, the aircraft is flown at top speed and then pitched up into a maximum climb. The aircraft then trades air speed for altitude. An F-104 “Starfighter” flew to an altitude of 103,395.5 feet in December 1959, using a zoom climb. Jet powered airplanes need to use the oxygen in the atmosphere to complete the combustion process (rocket powered craft bring their oxidizer along in the form of liquid oxygen or some other oxidizing chemical), so that naturally limits the ability of the engine to continue running, even with special fuels. For sustained flight outside of the atmosphere, you need a rocket engine system, which brings both the fuel
