The General Dynamics F-16 Fighting Falcon is an American single-engine supersonic multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superiority day fighter, it evolved into a successful all-weather multirole aircraft with over 4,600 built since 1976. Although no longer purchased by the U.S. Air Force, improved versions are being built for export. In 1993, General Dynamics sold its aircraft manufacturing business to the Lockheed Corporation, which became part of Lockheed Martin after a 1995 merger with Martin Marietta.