Final answer:
Based on the growth of the airline industry in the 1930s, the number of flights a year that airlines flew in 1930 would have been less than two million.
Step-by-step explanation:
In 1930, the number of flights that airlines flew each year can be estimated based on the growth of the airline industry during that time. In the mid-1920s, the first transatlantic flight was accomplished by Charles Lindbergh, which sparked the growth of the airline industry. By the end of the 1930s, the number of U.S. domestic air passengers had increased to nearly two million annually. Therefore, it can be inferred that the number of flights a year that airlines flew in 1930 would have been less than two million.