Impressed by the continued success of the B-52 in Iraq, the air force is again considering replacing the ancient eight TF-33 engines with four, or eight, more modern, powerful, fuel efficient and easier to maintain engines. The current TF-33 engines generate 17,000 pounds of thrust each, for a total of 136,000 pounds. These could be replaced by eight Pratt & Whitney JT8D-219 engines (22,000 pounds of thrust each, for a total of 176,000 pounds) or four GE F103 engines (51,000 pounds of thrust each, for a total of 204,000). The more modern engines, especially the four GE F103s, would be the most fuel efficient, reducing the number of air refuelings. Boeing, the manufacturer of the B-52, has been proposing new engines for the B-52 since the 1970s (when an earlier version of the GE F103 was proposed). But these proposals have been just as regularly turned down. At one point, the air force actually mounted a larger JT9 engine in place of a pair of the TF-33s, and flew the aircraft successfully several times. Before the current proposal, there were others in 1996, 1992 and 2002 (after seeing what the B-52 could do in Afghanistan). But what appears to be making new engines more attractive is the arrival of GPS guided bombs like JDAM, and the usefulness of having B-52s circle for hours on end, releasing bombs as needed to aid the battle below. This requires a lot of aerial refueling, and fuel delivered that way costs about $18 a gallon. This adds up, and the spreadsheets are now saying, "New Engines Are Good.". So a more powerful and fuel efficient engine would pay its way very quickly. The air force has also taken a close look at TF-33 maintenance costs. There are plenty of TF-33s in inventory (and also on C-141 transports, which are being stripped of their engines and junked). The KC-135 also uses TF-33s. But all these TF-33s have been rebuilt so many times, and are basically much older technology, that the potential maintenance cost savings grow each year as more efficient engine designs enter service. The air force is also well aware of the fact that the B-52 costs half as much to operate as the B-1. So if future battlefields must be patrolled by heavily loaded bomber, the cheapest way to do it is with a re-engined B-52.