USSR. Registered air letter sent from Moscow on September 17, 1928.

Cover of registered air letter sent from Moscow to Irkutsk, the first flight from Moscow to Irkutsk on September 17, 1928. Received in Irkutsk on September 22, 1928. Returned to Moscow for lack of the addressee, and end of expiration date. Received on January 12, 1929. Cover has a special air mail postmark of first flight from Moscow to Irkutsk on the back.