キャッスル作戦
An XB-47 was flown in the 1951 Operation Greenhouse nuclear weapons test. This was followed by a B-47B being flown in the 1952 test, Operation Ivy and the 1954 test, Operation Castle. A B-47E was then flown in the 1956 test, Operation Redwing. "Reflex" missions proved the long-endurance (eighteen hours) and long range capability of the B-47 and aircrews. These were "simulated strike missions against the then Soviet enemy".