The U.S. Air Force terminated a Boeing Co. contract to update the radar on its flagship AWACS radar surveillance aircraft after the company encountered major delays in developing hardware and software, according to budget documents. Instead of continuing the $76 million contract with Boeing, “the Air Force determined the best approach for providing this critical capability would be to replace the legacy radar processor and its related components,” Captain Hope Cronin, a service spokeswoman, said in an email. “Several companies responded to the Air Force’s request for information, and a request for proposal is currently being developed.” Boeing was on contract to provide improved radar digital signal processing “in a specific flight environment to meet a classified requirement,” for its E-3 Sentry Airborne Warning and Control System surveillance aircraft, Cronin said. The E-3 Sentry airborne warning and control system (AWACS), which are modified 707-320 commercial planes, are recognized by their saucer-shaped, rotating radar domes that can spot and classify aircraft as far as 250 miles away.