The Swiss Air Transport Company (Swissair) was formed on March 26, 1926, upon the merger of Balz Zimmerman's Basle Air Transport (Balair) and Ad Astra Aero, which was operated by Walter Mittelholzer. Both companies were originally founded in the early 1920's and operated a number of air routes between Switzerland and Germany. Swissair's fleet consisted of several aircraft built by Fokker, Dornier-Merkur, Messerschmitt and Comte. Later the company added Lockheed Orions, Curtiss-Condors, DC-2s and DC-3s to its fleet. At this time Swissair also became the first European airline to employ stewardesses.