The U.S. Navy is concerned about how safe their operating procedures and aircraft maintenance are after four aircraft (an F-14, an F-18 and two new F-18Fs) and five aviators were lost in a five week period recently. The value of the lost aircraft was $207 million. It's not unusual for aircraft losses to come in bunches, for no particular reason. For the last five years, naval aircraft have suffered 1.6 accidents per 100,000 flight hours. Operations in the war on terror increased navy and marine aviation operations to 972,000 hours in the 12 months since September 11, 2001 (11 percent more than the previous 12 months). As is usually done in situations like this, the navy will be checking the operating practices of all squadrons, particularly the ones with no accidents at all, in order to see if bad habits have anything to do with the aircraft losses. Carrier operations are, by their very nature, the most dangerous type of flying. However, the four aircraft lost were operating from land bases at the time.