WASHINGTON, Nov. 5 (Xinhua) -- The U.S. Air Force grounded nearly all its F-15 fighters Monday after a National Guard jet crashed Friday, apparently from structural failure.

    The unusual stand down comes as Air Force leaders acknowledge the wars in Iraq and Afghanistan have hurt readiness and cut into modernization of fighters, bombers, tankers and cargo jets, the Air Force said.

    Of the more than 700 F-15 jets, only aircraft flying missions over Iraq and Afghanistan are exempted from the flight suspension, according to Air Force spokesman Lt. Col. Ed Thomas.

    No date has been set for returning the jets to flight status.

    The crash of a Missouri Air National Guard F-15C jet occurred last Friday while four fighters were training in air combat maneuvers over southern Missouri.

    The pilot ejected and suffered a dislocated shoulder and broken arm.

    Known as the Eagle, the F-15 jets are based at several U.S. locations, including Langley Air Force Base in Hampton, Va., Seymour Johnson Air Force Base in Goldsboro, N.C., Robins Air Force Base in Georgia and Eglin and Tyndall air force bases in the Florida.