A US Air Force B-52 bomber drops a load of M117 750lb bombs in this undated file photo. The USAF's B-52 is a long-range, heavy bomber that can perform a variety of missions. B-52 bombers flying out of Fairford, England, supported the start of NATO's bombing campaign over Yugoslavia. The bomber is capable of flying at high subsonic speeds at altitudes up to 50,000 feet (15,166.6 meters). It can carry nuclear or conventional ordnance with worldwide precision navigation capability. — REUTERS