The unconventinal Ryan FR Fireball was the only fighter in operational service to be powered by both piston and jet engines: a true blend of old and new technologies. The Fireball was designed by Benjamin Salmon and William Immensusch and was also the first carrier aircraft designed with laminar-flow aerofoil and to have a fully flush-riveted exterior and metal skinned movable control surfaces. A radial engine was fitted in the nose while a turbojet was fitted in the rear fueslage: in flight, it was able to fly with either engine or with both. The Fireball made headlines when it became the first US aircraft to land under jet power on a ship (the escort carrier USS Wake Island) but the end of the war made the US Navy lose interest with the result being that most contracts were cancelled and only one squadron flew it until 1947 without it having ever seen combat at all.

First flight of the prototype XFR-1 took place on 2 December 1943 and it entered production as the FR-1. Large numbers of improved FR-2 units equipped with more powerful engines with water injection were cancelled after VJ Day while the experimental XFR-4 had another powerplant and flush side inlets in the forward fuselage.