The US Air Force has a serious shortage of spare engines for its F-15 and F-16 fighters. This is partly due to engines proving to be less reliable than expected (the F100 in particular), engines that were not ordered in large enough numbers, and unusually high numbers of "in combat" flight hours. There are enough engines for routine flight operations, but if the Air Force had to fight a major regional war (or two of them) it would quickly run out of engines. This would mean combat aircraft taken out of action by mechanical problems rather than enemy action. The Air Force admits that this shortage would cause problems in "sustaining" a force engaged in a second simultaneous war. The Navy reports similar shortages of fighter engines, that could result in entire carrier air wings being taken out of service if a regional war lasts for several weeks. . --Stephen V Cole