UPDATE: From the Steve Durst collection.
Group of 12 commemorative covers honoring flights of experimental aircraft including the X-15 and X-24B, each signed in ink by one or more legendary test pilots. Signers are: Chuck Yeager and Robert M. White, Scott Crossfield, Milt Thompson, Joe Engle, Pete Knight, Forrest S. Petersen, Bill Dana, Robert M. White, Tom McMurtry, John Manke, and Robert A. Rushworth (2). In overall fine condition.
