The Air Force just can't let go of the B-52.

In the world of heavy bombers, none has prevailed as long as the B-52 Stratofortress. The Cold Warrior joined the U.S. arsenal in 1954, eventually becoming part of a nuclear triad that, along with strategic missiles and submarines, was aimed at giving the Soviet Union pause. After the Berlin Wall fell, it slowly became an aerial jack-of-all-trades. With its long range, minimal operating cost and ability to handle a wider array of weapons than any other aircraft, it just didn't make sense to get rid of it.