What was the primary reason for the first flight around the world by US Army airmen?

The first flight around the world by US Army airmen was primarily motivated by the desire to demonstrate military aviation capabilities during a time when aviation was rapidly advancing. The flight, which took place in 1924, showcased not only the endurance and reliability of military aircraft but also highlighted the strategic importance of airpower in the context of military operations. This historic journey underscored the growing role of aviation in national defense and international reach.

While the other options touch on significant aspects of aviation history, they do not encompass the direct intention behind the flight. The mission was not about commercial aviation, although its success contributed to the aviation industry, nor was it specifically aimed at establishing airmail routes or mapping navigational air routes, even though these aspects became vital as aviation evolved. The emphasis was on showcasing military capabilities and enhancing the understanding of long-range flight in a military context.