In the film, the music is played during the opening sequence with fifty Heinkel aircraft, which were actually aircraft built by Spain's CASA. These aircraft had been flying in Spain's air force until 1968. These Spanish bomber aircraft also had Rolls-Royce Merlin engines; the aircraft during the war had Daimler-Benz engines. The aircraft had been obtained by Group Captain T.G. 'Hamish' Mahaddie. The famous opening sequence of the film was shot in March 1968 at Tablada Aerodrome (Seville Airport) in Andalusia, southern Spain. The film was produced by United Artists. There is a scene showing the deserted British Army vehicles at Dunkirk (Operation Dynamo), and a BBC Radio news broadcast (on 18 June 1940) announces "In the House of Commons this afternoon the Prime Minister Mr Churchill said - What General Weygand called the Battle of France is over. The Battle of Britain is about to begin", after which the "Aces High" or "Luftwaffe March" begins. The main titles were made by Maurice Binder. The German commanding officers inspect the fictional II./KG 545 bomber unit or "kampfgeschwader" (part of 2. Flieger-Division).