Danish Air Lines followed by Scandinavian Airlines
Det Danske Luftfartselskab A/S or DDL, trading in English as Danish Air Lines, was Denmark's national airline from 1918 until it merged to create Scandinavian Airlines System (SAS) in 1951. DDL was established on 29 October 1918, but started its first scheduled route on 7 August 1920.History
In 1920, the first airplane, a Flugzeugbau Friedrichshafen 49c, was acquired from the Deutsche Luft-Reederei (D.L.R.) in Germany. The airplane, with the previous German navy registration 1364, was almost new, and had been refitted for passenger transport before being delivered from Germany. It received the Danish registration letters T-DABA, and was used for the Copenhagen-Malmö-Warnemünde route in cooperation with the D.L.R. This plane was later returned to Germany, apparently because the transfer was not in accordance with the Versailles treaty.
In 1921 another F.F.49c plane from D.L.R. was acquired as a replacement for the first, with the previous German navy registration 3078. For unknown reasons this airplane used the same Danish registration T-DABA.
In the early 1920s, the airline relied on four chartered Fokker-Grulich F.III aircraft, but also Dornier Komet, 
Junkers F.13s and the Airco DH.9.In 1926 the first of a total of four Farman F.121 Jabiru 4-engined commercial airliners, seating nine passengers, were acquired. It was registered as T-DOXB, and was used on the Copenhagen to Amsterdam line. Amsterdam was a hub with connections to London and Paris. The aircraft were withdrawn from use in 1928 and 1929, and broken up by 1931.
In the late 1920s, Fokker F.VII single-engined airliners replaced the somewhat problematic and expensive to operate Farmans.In 1933, the airline got the first of two 16 passenger Fokker F.XII airliners. They were built under license by Orlogsværftet. Both aircraft were scrapped by 1946.
In 1938, two Focke-Wulf Fw 200 Condor 26 passenger airliners were acquired. One, Dania, was seized by the British after Denmark was invaded by German forces in 1940, and damaged beyond repair in 1941. The other, Jutlandia, survived the war and continued in DDL service until damaged beyond repair at Northolt in 1946. 
In 1946, the airline started intercontinental traffic in cooperation with Det Norske Luftfartselskap and Svensk Interkontinental Lufttrafik in an SAS Agreement. On October 1, 1950 representatives from the three airlines signed a consortium agreement where they appointed SAS to run the airline operations. DDL thus changed status from being an active airline into becoming a holding company for the Danish interests within SAS.