Basic Military Training: a Comprehensive Manual of Military Training, Volume I. Military Service Publishing Company, 1921.

HOW TO HIT BACK AT DIVE BOMBERS

When your weapon is fired it takes the projectile a definite time, called the "time of flight," to travel to the target. If you fire at a moving target, such as an airplane, the target will continue to move during the time of flight of the projectivle. In order to hit the target, you must aim at the point at which the target will arrive at the time of flight of the projectile.