The heat dust and sand are taking a toll on U.S. Air Force aircraft serving in Iraq. While this can be handled with more work by the maintenance crews, the air force has found it more efficient to rotate aircraft out of Iraq periodically. The air force won't say how often fresh aircraft, particularly F-16s, are brought in, but apparently several hundred F-16s have already done a tour in Iraq. While pilots and ground crews come in three months at a time, the aircraft stay longer, often a year or more. It all depends on how much an aircraft has gotten beat up by the sun and sand.