Quinjets are hybrid supersonic contragravity/jet/fan aircraft capable of speeds in excess of mach 3/2200 mph with a range of 6,000 miles.
They were designed by Henry McCoy and built by Lockheed-McCoy, primarily for US governmental agencies (mostly SHIELD and the USAF) for use as small (very small) transports and close air support (CAS).
Quinjets are remarkably cheap due to a superhuman intellect’s design and the use of fabbers for many crucial components. L-M makes most of its money on civilian lifters.

Quinjet A: standard model, as seen in Marvel’s the Avengers.
Quinjet B: CAS model, some armoring and passenger room replaced by more dakka. Not nearly the tank-killer the A-10 is.
Quinjet C: ‘civilian’ (unarmed) model used by the Dept. of Mutant Affairs, the Xavier Institute, and McCoy’s personal jet.
“Quinjet X”: (Lockheed-McCoy-Stark) an experimental model with the jet engines replaced by an Arc reactor-powered repulsor system, sealed for vacuum, with limited life support and radiation shielding (rated for LEO only). Initial flight tests completed successfully. Gearing up for an International Space Station supply mission. Capable of surviving hypersonic+ speeds only outside of the atmosphere (~80 miles+ up).



S.H.I.E.L.D. Los Angeles RTrimmer