a <#postalcard=postal card> intended to be sent by <#airmail=air mail>.  <#scott=Scott> numbers begin with UXC.

privately printed stamps issued for a balloon flight in 1877 and an airplane flight in 1911.  see <#buffballoon=Buffalo Balloon> and <#rodgers=Rodgers Aerial Post>.  <#scott=Scott> numbers are prefixed with CL.

a <#stamp> paying the postage for <#airmail=air mail>.  Since 1977 Air Mail stamps are issued only for international air mail.  <#scott=Scott> numbers for air mail stamps are prefixed with C.

a <#stampenv=stamped envelope> intended for <#airmail=air mail> service.  <#scott=Scott> numbers for air mail stamped envelopes and <#aerogram=aerograms> are prefixed with UC.

see <#buffballoon=Buffalo Balloon> and <#rodgers=Rodgers Aerial Post>.