"... Even so, the X-5 had vicious
spin characteristics arising from the aircraft's flawed aerodynamic layout, particularly a poorly positioned tail and vertical stabilizer which, in some wing positions, could lead to an irrecoverable spin. 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."
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