[1] Although superficially similar, the X-5 was much more complex than the P.1101, with three sweep positions: 20°, 40° and 60°, creating an inflight "variable-geometry" platform.

This violent stall / spin instability would eventually cause the destruction of the second aircraft and the death of its Air Force test pilot in 1953.

[2] The unfavorable spin characteristics also led to the cancellation of tentative plans by the United States Air Force to modify the X-5's design into a low-cost tactical fighter for NATO and other foreign countries.

The X-5 successfully demonstrated the advantage of a swing-wing design for aircraft intended to fly at a wide range of speeds.

Despite the X-5's stability problems, the concept was developed to an outboard rather than inboard hinge,[4] and was later successfully implemented in such aircraft as the General Dynamics F-111 and Grumman F-14 Tomcat, the Mikoyan Gurevich MiG-23 and MiG-27, the Sukhoi Su-17/20/22 and Su-24, the Tupolev Tu-22M and Tu-160, the Panavia Tornado and the Rockwell B-1 Lancer.