Built as B-57B 53-3918. Extensively modified by General Dynamics with higher power engines, extra wingspan etc as RB-57F 63-13295. Later redesignated WB-57F. To AMARC on 26 July 1972, but retrieved from storage in May 2011 and rebuilt to flying condition using from parts from 63-13290 and 63-13293. In July 2013 it was delivered to the NASA as WB-57F N927NA.