The F-15J is a twin engine air superiority fighter. Two of them were built in Saint Louis, United States, but the majority (139 aircraft) was manufactured in Japan under license by Mitsubishi Heavy Industries. Based on McDonnell Douglas F-15 Eagle, it is fitted with several indigenous components, including the electronic countermeasures system and the Japanese-built AAM-4 missile, a modified version of U.S. made AIM-9 Sidewinder.