In the US: Wings

Wings are perhaps the most universal symbol of flight, and early US Air Mail stamps have incorporated wings into their design.US C17 Air Mail Stamp
The 1932 US Air Mail Issue, C-17

A new air mail rate of 8 cents per ounce went into effect July 6, 1932. This stamp was issued for this rate on September 26, 1932 in Washington, D.C.US C-19 Air Mail Stamp
The 1934 US Air Mail Issue, C-19

This stamp was issued in 1934, repeats the design of the 1932 issue.US C24 Air Mail Stamp Trans-Atlantic
The 1932 US Trans-Atlantic Issue, C-24

This stamp was issued on May 16, 1939 to commemorate the beginning of Trans-Atlantic air mail. The winged-globe Insignia from earlier designs is shown above 2 ships on the Atlantic.