Per a recent article in Defense News:

"According to the Navy, 53 percent of all Navy aircraft can't fly - about 1,700 combat aircraft, patrol, and transport planes and helicopters. Not all are due to budget problems - at any given time, about one-fourth to one-third of aircraft are out of service for regular maintenance. But the 53 percent figure represents about twice the historic norm.

"The strike fighter situation is even more acute and more remarkable since the aircraft are vitally important to projecting the fleet's combat power. Sixty-two percent of F/A-18s are out of service; 27 percent in major depot work; and 35 percent simply awaiting maintenance or parts, the Navy said."