Ford 4-AT Trimotor

Credit - Courtesy of Aerofiles

Boeing 40-C mailplane

Credit - FAA

William MacCracken and Herbert Hoover

Credit - FAA

DeHavilland 4B

Credit - United Airlines Archives

National Air Transport plane

Credit - United Airlines Archives

Ryan-M1 plane

Credit - Courtesy of Aerofiles

Douglas M2 plane

Credit - Courtesy of Aerofiles

Airmail pickup around 1927

Credit - ") 2001 National Air and Space Museum, Smithsonian Institution (SI Neg. No 89-147)"

Original air mail route map

Credit - Air Mail Pioneers

"U.S. airways as of Dec. 31, 1927"

Credit - ") 2001 National Air and Space Museum, Smithsonian Institution (SI Neg. No 89-7060)"