The U.S. Navy experimented with the use of airships as airborne aircraft carriers, developing an idea pioneered by the British. The USS "Los Angeles" was used for initial experiments, and the and , the world's largest at the time, were used to test the principle in naval operations. Each carried four F9C Sparrowhawk fighters in its hangar, and could carry a fifth on the trapeze. The idea had mixed results. By the time the Navy started to develop a sound doctrine for using the ZRS-type airships, the last of the two built, USS "Macon", had been lost. The seaplane had become more capable, and was considered a better investment.