[4] Providing adequate stability and control for aircraft flying at high supersonic speeds was only one of the major difficulties facing flight researchers as they approached Mach 3.

Constructed of stainless steel and a copper-nickel alloy called K-Monel, and powered by a liquid propellant (alcohol and oxygen) two-chamber Curtiss-Wright XLR25 2,500 to 15,000 lbf (11 to 67 kN) sea level thrust, continuously throttleable rocket engines, the swept-wing Bell X-2 was designed to probe the supersonic region.

[3] Following a drop launch from a modified B-50 bomber, Bell test pilot Jean "Skip" Ziegler completed the first unpowered glide flight of an X-2 at Edwards Air Force Base on 27 June 1952.

By the time of his ninth and final flight in late July 1956 the project was years behind schedule, but he had established a new speed record of Mach 2.87 (1,900 mph, 3,050 km/h).

Moreover, simulation and wind tunnel studies, combined with data from his flights, suggested the airplane would encounter very severe stability problems as it approached Mach 3.

Some cited his lack of experience with rocket planes, but, as historian Chris Petty notes, "he had in fact flown the complex profile almost perfectly, but this, combined with additional seconds of thrust from the XLR25 [engine], had carried the X-2 well beyond the envelope of knowledge and into the uncertain stability predicted by the GEDA [Goodyear Electronic Differential Analyzer computer].

Petty quotes Base commander General Stanley Holtoner: "I think that every supervisory guy from me on down has criticized himself, because if we had told this boy [Apt] to stop at a specific speed, this wouldn't have happened.

According to The New York Times reporting on the event, Everest had criticized the relatively new detachable capsule, maintaining that "some safety had been sacrificed in preference to delaying the X-2 flight tests while the escape mechanism was modified.

"[14] While the X-2 had delivered valuable research data on high-speed aerodynamic heat build-up and extreme high-altitude flight conditions (although it is unclear how much, as the unmanned Lockheed X-7 and IM-99 were among the winged vehicles operating at comparable or higher velocities in this era), this tragic event terminated the program before the National Advisory Committee for Aeronautics could commence detailed flight research with the aircraft.