History started on May 3rd, 1923 when Dr. Walter Bardas-Bardenau
was allowed to found an Austrian Air transport company.
The original share capital was one billion "inflation"crowns, 49% of them were owned by Junkers Flugzeugwerke, 50% by the Austrian Railways traffic Institute (österreichische Eisenbahn-Verkehrsanstalt) and 1% by Bardas-Bardenau.
The first airplanes arrived on May, 14th 1923, coming from Munich. They were Junkers F 13 planes, a type which was the bakbine of Oelag for several years.Oelag was part of Transeuropa-Union, which was Junkers dominated. In the foreground of all activities never stood who flew which route at which time, but that the whole service was running, which included very often the exchange of flying equipment and pilots. Due to allied restrictions Austria was not allowed to build and own "big" planes after WW I, so it happened, that the baptism of the trimotor aircraft Junkers G-23 to "Österreich" (Austria) became a "funny" event, because the plane was built in Sweden, had a Swiss registration and was flown by a German pilot.
After Munich and Budapest also Nuremberg, Graz and Klagenfurt were integrated into the network, and during high season also St. Wolfgang could be reached with the "seaplane" A3 from Vienna. On September 15th, 1926 Transeuropa-Union was rejected, and it came to a radical break down of services. Only after a subsidy of one million (Austrian) schilling in 1927 better times arrived. In March of the same year Oelag got its first own trimotor plane, a Junkers G-24, a plane which had a heating and radio onboard. With it Oelag started the service Vienna-Prague-Dresden-Berlin.
The network expanded also to the south and in April 1927 the route from Vienna via Graz to Klagenfurt was extended to Venice. Also a line from Vienna via Salzburg to Innsbruck was inaugurated, which was expanded to Constance at August 4th. On June 1st 1928 a Junkers G-31 (registration A-46) arrived in Vienna and was used for the express line Vienna-Berlin. The price was 175 schilling and flying time was three and a half hours. This plane had a kitchen onboard, also a toilet and a washing room. Windows were allowed to open and close "after demand", but making photos was not allowed, also it was strictly prohibited to threw out things. In April 1931 Oelag flew also the line Munich-Innsbruck-Bozen-Trient-Milano and so they were crossing the Alps - a sensation in these days. A month later the express line from Berlin via Vienna was extended to Budapest.
There was only one non-Junkers airplane in scheduled service with Oelag: A Douglas DC-2, which was mainly used for governmental purposes. In March 1936 the plane was sold to Swiss Air.
Because of the world economic crises the number of passengers fell, and because of the relatively old fleet the company was not well equipped for the competition. 1934 was a very bad year. On March 29th, 1935 the first Junkers Ju 52/3m (a trimotor which became famous as "Tante Ju" in the years after) arrived at Vienna airport at Aspern. Because of new airplanes the situation became better and better and Oelag became number four under European airlines with a million seat-kilometers (after Lufthansa, KLM and Air France); this was almost 10 percent of all airlinekilometers in Europe.
From 1938 on it was planned to bring new money into the company over the following five years. Also the first long-distance flights to Rome, Paris and London should be inaugurated and new planes should be bought, after the Ju-52/3m also four engine planes Junkers Ju 90. This plan passed the general assembly in January 1938 and on March 8th also the federal Chancellary agreed.
But everything came different and Austria was occupied five days later by German Reich and did not exist for the following seven years. On March 28th two further Ju52 arrived, and they had probably till an Austrian registration (one was OE-LAS), but Oelag was already under control of Lufthansa. Officially Lufthansa took over Oelag on January 1st, 1939. Oelag was cancelled from the commercial register Vienna on June 16th, 1939.