While U.S. naval forces are at historically average levels for ships at sea (40-50 percent, with 30-35 percent deployed to distant locations), the units that are in combat zones are working a lot harder. This is particularly true of carrier aviation. Normally, a carrier averages about 115 hours a day (of aircraft in the air.) During the peak of the campaign in Afghanistan, this averaged 250 hours a day and the average is currently 190 hours a day. This puts a lot of stress on pilots and maintenance crews. It also causes supply and budget problems, as more flying hours increases the demand for spare parts. In late 2001, there were some 60,000 navy and marine personnel in the Middle East.