File:US stamp 1918 24c Curtiss Jenny C3-Fast-Plane Var.jpg
C115 - 1985 44c Transpacific - Mystic Stamp Company
FDR, Farley, Amon Carter and Transpacific First Flight Covers
C22 - 1937 50c Trans-Pacific carmine - Mystic Stamp Company
Airmail stamp - Wikipedia
C20 - 1935 25c Trans-Pacific blue - Mystic Stamp Company
Category:U.S. territories on stamps - Wikimedia Commons
1935-1937 China Clippers #C20-C22 - Airmail Stamps - USA
United States airmail service - Wikipedia
China Clipper - Wikipedia
China Clipper - Wikipedia
C20 - 1935 25c Trans-Pacific blue - Mystic Stamp Company
C20 - 1935 25c Trans-Pacific blue - Mystic Stamp Company