 Complete the following phrase:  The history of Scandinavian Airlines System SAS from 1933 to 1951 covers the first attempts at transatlantic travel, the establishment of a consortium and finally the establishment of the consolidated SAS. Aerotransport, the national airline of Sweden, and Det Norske Luftfartselskap DNL, the national airline of Norway, both started planning transatlantic routes in the mid-1930s. By 1939, negotiations were started with Det Danske Luftfartselskab DDL of Denmark, and by 1940 services were to begin. Because of the 