Probably that helped a lot during the romantic interludes in the film.
Taylor was between his marriages to Barbara Stanwyck and Ursula Thiess and was involved with Parker at the time Above and Beyond was being filmed. Paul Tibbetts who's marriage was put under an incredible strain due to the security surrounding his assignment. Robert Taylor and Eleanor Parker play Colonel and Mrs. Above and Beyond concentrates on the pilot of the B-29 that actually did the deed. The actual development of the atomic bomb was documented in films like The Beginning or the End and in Fat Man and Little Boy.