Can a company be both an airplane manufacturer and an airline?
Another historical perspective: Junkers helped to found and participated in dozens of airlines in the early 1920s. This helped to boost demand for his products (mainly the F-13, but all started with two converted military two-seaters).

That was everything but unusual: Many aircraft factories, among them Albatros and Sablatnig in Germany, tried to shift their products after the cessation of hostilities by founding airlines.

Generally, when a city wanted to be connected to the new air travel network, it would supply an airfield and some capital and the aircraft company would be happy to contribute aircraft and personnel. This way, dozens of airlines providing mostly local connections were operating in the early Twenties in Europe and competition would drive down prices and increase demand. Therefore, all those airlines were unprofitable and successfully lobbied for government support, which grew from year to year. But also Junkers was not profitable and had to be supported by government loans.

By 1925, 40% of all civil air traffic worldwide was flown on Junkers airplanes and Junkers Luftverkehr AG completely or partially owned many of the airlines operating its aircraft. The failure of Junkers to repay government loans at the end of 1925 meant that ownership of those shares was transferred to the German government which moved swiftly to consolidate the German airlines into Luft Hansa, thus ending the price war and greatly helping to reduce the subsidies.

By resolving to only subsidize one single airline, the national flag carrier, Governments effectively ended the habit of aircraft manufacturers to operate airlines. Specific legislation was not needed.