The Boeing B-9 bomber was the earliest plane based on the Monomail design. It had a top speed of 186 mph and could outrun the fighters of the day by 5 mph. The monoplane bomber reached this speed although it had a five-person crew (in open cockpits) and carried a 2,400-pound bomb load.

Boeing built the YB-9 prototype bombers at company expense to show their design potential to the military. This high-speed aircraft inspired other airplane manufacturers to launch a new generation of bombers, such as the Martin B-10. Because fighters were expected to be faster than bombers, the B-9 also led to the first monoplane fighters.