From Wikipedia

Baiting the Bear

During the Cold War the United States and United Kingdom on one side and the USSR on the other kept nuclear-armed strategic bombers ready to launch at a moment's notice as part of the deterrent strategy of Mutual Assured Destruction. Most strategic bombers of the two superpowers were designed to deliver nuclear weapons. For a time, B-52 Stratofortress bombers were kept in the air around the clock, orbiting fail-safe points near the Soviet border. The RAF's V-bombers were directed against targets in European Russia and would have been able to reach and destroy cities like Kiev or Moscow before US bombers.