Our great president was lucky enough to do anything during WW2 as he was practically blind, among other 4F-making problems. Still, like others who weren't up to scruff for fighting, he signed up anyway. Instead of being turned down, RR was used effectively for moral building public appearances and training films like JAP ZERO.
In this, the "Japs" aren't the real enemy, Reagan is. All too quick on the trigger in his fighter, he nearly downs fellow American Craig (Peter Gunn) Stevens.
This film was meant to help train pilots to wait until they could make out the enemy, insuring they weren't firing on a friend by mistake. The "Zero" in the title tells Regan to look at not only the shape of the plane, but the telltale meatball insignia. Note that this was not the ONLY training pilots received on the subject, but it was thought that a dramatization could help push home the point. Firing on and even downing friendly aircraft was a serious problem (as friendly fire is to this day).
Reagan manages a sympathetic portrayal as the young pilot who almost made a fatal mistake. The film is short, crisp, and using Hollywood veterans behind the cameras, well made.