posted 07-20-2026 09:38 AM               

The M2-F1 Lifting Body aircraft is at left, alongside the M2-F2.

The Lifting Body aircraft were part of a long line of historic experimental aircraft flown at the Air Force Flight Test Center, Edwards AFB, CA, that included the X-1, the first aircraft to exceed the speed of sound, and the X-15 that set speed and altitude records.

The Lifting Body aircraft tested the concept of wingless spacecraft reentering from space and landing like an airplane, but the concept proved impractical and the Lifting Body program ended with the X-24B's final flight in 1975. However, some concepts learned from the Lifting Body program were incorporated in the space shuttle program.

This first cover in the set is autographed by the nine pilots who piloted at least one of the three M2 aircraft in free flight. Included are Chuck Yeager, the first pilot to exceed the speed of sound, and X-15 pilots Milt Thompson and Bill Dana.

Also included are five autographs by John Manke, who piloted four of the six Lifting Body aircraft, and an autograph by X-24B pilot Dick Scobee, who perished on Challenger.

At top, M2 cover autographed by the seven M2-F1 pilots who flew at least one untethered free flight. Below, M2 cover autographed by the four M2-F2 pilots

At top, M2-F3 flight cover autographed by the four M2-F3 pilots. Below, HL-10 flight cover autographed by the five HL-10 pilots

At top, X-24A flight cover autographed by the three X-24A pilots. Below, X-24B flight cover autographed by the six X-24B pilots

This set of seven covers contain autographs of all 14 pilots who flew at least one of the six Lifting Body aircraft.

The autographs in the set resulted from many mailings to various locations, with most from the Air Force Flight Research Center at Edwards AFB. The difficulty of this long-time, multi-autograph, multi-mailing project, makes this set very rare and possibly one-of-a-kind.