Lieutenant Thorne's pet lion in the film was based on two real lions who served as mascots for the Lafayette Escadrille, a squadron made up of American volunteers prior to the U.S. entering the war. The two lions were named "Whiskey" and "Soda."
Although Lieutenant Thorne is said to have 42 victories and another American is said to have 44, in reality the top American ace of World War I, Eddie Rickenbacker, had far less. He finished the war with 26 victories. However, there were pilots from other nations who amassed many more, led by Manfred von Richthofen ("The Red Baron") who had 80 victories before he was killed.
Several times the Americans refer to their German opponents as 'heinies.' This was a derogatory term, short for "Heinrich."
The "ARC" lapel pins on Nancy's uniform stand for "American Red Cross."