Test Planes Wiki

The second X-4 Bantam in flight[1]

The X-4 was an experimental aircraft intended to evaluate flight conditions at transonic speeds.


Development of the X-4 began on5 April 1946, when the US Army Air Force's Technical Service awarded Northrop Aircraft Corporation a contract for construction and preliminary flight testing for a pair of XS-4 research aircraft, as part of project MX910.[2]


  1. War thunder X-4
  2. Miller, Jay. The X Planes X-1 to X-45. Midland Publishing. 2001. ISBN 1 85780 109 1 Page 80