Like the D.H. 108, the two-beam Northrop X-4 was one of the postwar X-aircraft designed in the United States after World War II to fly in research programs that explore the challenges of high-speed transonic flight and beyond. It had aerodynamic problems similar to those of the D.H.108, but both examples X-4 survived their flight test programs without serious incidents by about 80 total search flights from 1950-1953, only reaching top speeds of 640 mph (1,035 km/h). Many early constructions could not provide effective pitch control to compensate for the missing stabilizer. Some examples were stable, but their height could only be controlled with engine power. Others could go up or down safely and uncontrolled if they were not treated with care. These gave designs without tail the reputation of instability. It was only with the subsequent success of the tailless delta configuration in the jet era that this reputation was widely recognized as undeserved. Stability can also be artificially guaranteed. There is a trade-off between stability and manoeuvrability. A high degree of manoeuvrability requires a low degree of stability. Some modern high-tech fighter jets are aerodynamically unstable and rely on fly-by-wire computing control to ensure stability.
The Northrop B-2 Spirit fly wing is an example. The French mirage series of supersonic jet fighter jets was an example of a tailless delta configuration and has become one of the most produced Western jets. In contrast, the Delta Wing Fighter equivalent of the Soviet Union, the Mikojan-Gurevitch MiG-21, has a tail stabilizer. The solution solution is to provide large elevator and/or Elevon surfaces on the rear edge of the wing. If the wing is not heavily swept, they must produce large control forces, as their distance from the aerodynamic center is small and the moments less numerous. Thus, in pitching manoeuvres, a type without a tail may experience a higher air resistance than its traditional equivalent. In a heavily curved delta wing, the distance between the rear edge and the aerodynamic center is greater, so that the enlarged surfaces are not necessary.