Actual graphic from FM 44-8: Small Unit Self-Defense Against Air Attack, a very interesting document that was first issued at a time (1981) when the U.S. was not so confident in its ability to maintain air superiority. The manual begins with the following:
In the past US Army forces have fought on the battlefield with little concern about attack from the air. Troops and convoys were occasionally bombed or strafed with machinegun or cannon fire, and our forces enjoyed the luxury of air superiority most of the time.
The days of total supremacy are behind us. Our potential enemies could have more aircraft than we do, and we can expect that they will gain control of the airspace over sectors of the battlefield from time to time.
Don’t tell that to Secretary Gates; you might lose your job.