"Eagle" started Sea trials on 31 October 1951, with initial flying trials starting on 14 February 1952 and the ship being accepted into service on 1 March 1952. "Eagle" continued to work up her crew, embarking an initial air wing equipped with two squadrons of Supermarine Attacker jet fighters, two squadrons of Fairey Firefly anti-submarine aircraft and a squadron of Blackburn Firebrand attack aircraft, and in September 1952, took part in the big NATO naval exercise, Exercise Mainbrace off the coast of Norway and Denmark.