The U.S. Federal Aviation Administration (FAA) said it is prohibiting U.S. airlines from flying over Iraq because of security concerns.
The FAA announced the ban on August 8, citing the "potentially hazardous situation" created by fighting between militants and Iraqi security forces and their allies.
The ban comes as the United States launched its first air strikes in Iraq against Islamic State militants who have seized swaths of territory in northern and western Iraq.
The FAA had previously restricted flights over Iraq to altitudes no lower than 10,000 meters.
The ban comes just three weeks after a Malaysia Airlines plane with nearly 300 people on board was shot down over eastern Ukraine, allegedly by pro-Russian separatists.
Based on reporting by Reuters and AP