Flight 138 of the North American X-15 was a test flight conducted by NASA and the US Air Force in 1965. Piloted by Joe H. Engle it reached an altitude of 85.5 km. June 29, 1965 at 18:21 UTC · Launch Successful North American X-15 — United States Air Force, to Suborbital Edwards Air Force Base, Air launch to Suborbital flight Crew: Joe Engle Program: X-15 Data: Launch Library 2, The Space Devs. Image via The Space Devs.