The USS Antietam (CV/CVA/CVS-36) was one of 24 Essex-class aircraft carriers built during World War II, and the first carrier to be fitted with an angled deck. This innovative feature, made possible by the addition of a port sponson, effectively allowed aircraft to take off while others were simultaneously landing. This film was made to acquaint naval aviators and deck crew with this new feature. Also shown in the film is USS Coral Sea (CV/CVB/CVA-43), a Midway-class aircraft carrier which was converted in 1957.The "angled deck" was not a U.S. innovation, but was developed by the Royal Navy. Excellent background in this U.S. Naval War College pdf The Development of the Angled-Deck Aircraft Carrier. Nice discussion of innovation.