(Reuters) Pratt & Whitney (East Hartford, Conn.), the engine making unit of United Technologies Corp. received a $431 million supplement to its U.S. Air Force contract to make engines for the F/A-22 Raptor fighter aircraft. The supplement was added to an existing $168 million long lead production contract issued in 2003, making the overall contract worth roughly $600 million. The F119-PW-100 engine contract calls for 42 installed engines for delivery in 2006, as well as spare engines, spare parts and support services. The F/A-22, being built by Lockheed Martin Corp. is expected to replace the F-15C as the top U.S. air-to-air combat plane.