Dennis I have always like "Sahara" because of the "Lee's" and "Grants" in that movie. I can't think of another movie with them in it. I would say that shot was pure Hollywood. Certainly the tracking abilities of the M-3 turrets were not capable of training on a plane in flight. Maybe stationary and the plane flying into the path of the .37mm shell, but not tracking it like a duck with your shotgun.

However, remember that "Sahara" was made during the War. So suggesting that the american equipment had abilities that they really didn't was probably intentionally built into the movie. One of the things that was top secret during WW II and lead to maybe this scene being in the movie was the developement of a proximity fuse for use by normal artillery against aircraft. The navy used a lot of these in the Pacific, Naval guns, primarily 5 inch guns on destroyers, being used as anti-aircraft. But, I don't think that they developed these proximity fuses for anything smaller than the 5 inch gun. And by the time that those were developed the M-3 "Lee's" and "Grants" had long been replaced by the Sherman's which mounted 75 mm and 105 mm guns in the turrets. Oddly that is the reason that you see those tanks in "Sahara", because when the movie was made they had already been replaced by the "Shermans", although they, the M-3's, were historically accurate for North Africa.

Another "Hollywoodism" in that movie is at the end of the movie Bogey calls the names of his dead and says 'They held them at El Alamein". Well the 1st battle of El Alamein in which the British held the Germans was in the summer of 1942. Americans didn't land in North Africa until November 1942. So what force was Bogey with to be fighting against germans with the British in Libya and Egypt during the summer of 1942? The Battle of Kasserine Pass wasn't until February 1943 across the Continent from El Alamain.