Stamped cachet: "Aviation History, 1911-1938 - Glenn L. Martin Flies First Plane into Clay Center, Nebraska, 1911. 1911 - Pusher type plane. 1938 - Glenn Martin today. Martin and his plane. First Air Mail Flight, May 19, 1938."
[First flight air mail cover addressed to William E. Boeing], [2005-10-06-B_text_247]. Museum of Flight Digital Collections, accessed 05/12/2025, https://digitalcollections.museumofflight.org/nodes/view/8890
![[First flight air mail cover addressed to William E. Boeing]](/img/placeholder.gif?1761251355 "[First flight air mail cover addressed to William E. Boeing]")