The FAA announced the ban Friday, citing the "potentially hazardous situation" created by fighting between militants and Iraqi security forces and their allies.
The ban applies to all U.S.-registered planes except those operated by foreign carriers and to FAA-licensed pilots. There is an exception for flights operated with U.S. government permission and for emergency situations.
The FAA previously had limited flights over Iraq to altitudes no lower than 30,000 feet.
The ban comes just three weeks after a Malaysia Airlines plane with nearly 300 people on board was shot down over eastern Ukraine.
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