May 18 (Reuters) – The U.S. Air Force intends to award a contract in 2024 for its sixth-generation fighter jet as it races to retain its edge against rapid advances in Chinese military technology, the service said on Thursday. Lockheed Martin Corp (LMT.N), Boeing Co (BA.N) and Northrop Grumman Corp (NOC.N) are expected to compete for the Next Generation Air Dominance program, which will replace Lockheed's F-22 Raptor with a fighter built to battle alongside drones. Boeing, Lockheed and Northrop did not immediately respond to requests for comment. The Air Force released a classified solicitation to industry on Thursday laying…