Which industry began to form in the 1930s? the railroad industry the cruise ship industry the airline industry the Disney resorts

The answer is airline industry.

The first passengers airlines actually first created in 1919, but at that time, the amount of money involved still hasn't big enough to be considered as industry.

The market for airline started to show a promising future in 1930s, where they started to obtain more than 6,000 consumers per year. 4 Years after that, they started to obtain a staggering increase to 450,000 consumers per year.