This is an old - not maintained - article of the AEIOU.
In the Austria-Forum you find an updated version of this article in the new AEIOU.
Air Mail: During the first World War air units carried parcels for the imperial army mail ("Fliegerpost"). Military aircraft transported civilian air mail for the imperial Austrian postal service from March 31, 1918 on the route Vienna- Lvív- Kiev, at first, private mail was only transported to or from Lvív. The first air-mail postal stamps were overprint makeshifts. Austria was the first country in the world to introduce a civilian air mail service, followed by the USA, which introduced a similar service 6 weeks after Austria. Owing to the war the air mail service was suspended on October 15, 1918.