On 6 January 1926 the two companies Deutsche Aero-Lloyd AG (DAL) and Junkers Luftverkehr AG merged into Deutsche Lufthansa AG. Lufthansa adopted a house flag as early as 1930. This showed on a blue field a yellow St. Andrew's cross, fimbriated yellow, and centred on it a yellow disc, fimbriated yellow, bearing a blue crane. This flag was used until 1945.
After WWII, Deutsche Lufthansa was re-established again 1954 as a successor to the Company for Air Traffic Demand (Gesellschaft für Luftverkehrsbedarf) which had been established in 1953. It readopted its former house flag.
The word "Hansa" stands for trade and traffic and bears memory to the Hanseatic League. (...) The original flag design was registered in 1929 as house flag in the International Patent Office of Bern, Switzerland.
Source: Sonder-Edition des Journals "Luftfahrt": Deutsche Lufthansa 1926-2001, Frankfurt am Main, July 2001.
Luft means air, Hansa is probably a reference to the Hanseatic League. The Lufthansa (1926-1933 "Luft Hansa") was founded in 1926 as a merger of two airlines, the Deutsche Aero Lloyd (DAL) and the Junkers Luftverkehr, so I guess that the "Hansa" refers to this merger as similar to the "merger" of the Hanseatic cities into the Hanseatic league. The history of the "crane logo" is shown at the Lufthansa website.
The symbols (logotype) and the flag of Lufthansa are registered as a trademark. The official flag is still the blue "house flag" (see image above) with saltire and crane. The crane has been modified four times graphically. Since 1978, the logo flag is orange with blue lettering "Lufthansa" and blue crane logo in use. It is still used for decorations on the airports and city offices.
It was a blue swallow tail pennant, with yellow stripes at the top and bottom edge, both stripes charged with two black lines, slightly shifted to the hoist on a yellow disc fimbriated black the crane.
It was a blue pennant, slightly shifted to the hoist on a yellow disc fimbriated black the crane.
Deruluft had been a joint German-Soviet airline from 1921 to 1937. There appears to be two versions of the flag: one modeled closely after the Lufthansa flag, as illustrated here, and a simplified version without the fimbriations, as illustrated on Victor Lomantsov's Russian Flags website.