Last July, a U.S. B-52 bomber crashed off Guam. The subsequent investigation revealed that the cause was mechanical failure. The item that failed was the horizontal stabilizers (the flaps on the small wing type structures in the tail). The horizontal stabilizers control pitch (which direction, up or down, the nose of the aircraft is pointing). The B-52 was descending when the horizontal stabilizers failed, and this happened at a low altitude (about 8,000 feet). It was the low altitude that caused the aircraft to be lost. The crew became aware of the problem quickly enough, but they didn't have enough time (altitude) to correct the downward pitch of the aircraft. Because they were descending, they were moving pretty fast. The air force is still searching the ocean bottom for more parts to determine exactly how the horizontal stabilizers failed, and determine what can be done to other aircraft to prevent a similar accident.
Despite losses like this, the B-52 has the lowest accident rate of (less than 1.5 per 100,000 flying hours) of all American heavy bombers. The B-1s rate is 3.48. Compared to the supersonic B-1 and high-tech B-2, the B-52 is a flying truck. Thus the B-52, despite its age, was the cheapest, safest and most reliable way to deliver smart bombs.
With a max takeoff weight of 240-250 tons, the BUFF (Big Ugly Fat Fellow) is basically a large aircraft designed to carry bombs. Lacking the supersonic speed of the B-1, or the stealth and automation of the B-2, the B-52 can carry up to 150 tons of fuel, and normally carries 12-20 tons of bombs (max load of 35 tons). What made the B-52 so useful in Afghanistan and Iraq was its ability to stay in the air for so long. Since it can refuel in the air, the B-52 can fly anywhere in the world with a load of bombs or missiles.