The Federal Aviation Administration has issued a notice to airmen prohibiting airlines based in the United States from flying over Iraqi airspace.
The decision comes as safety concerns about military conflict in the area continue to rise.
The ban comes as US military forces begin airstrikes against militants in northern Iraq.
A previous warning urged pilots to fly at least 30,000 feet above Iraq because of the conflict between Iraqi security forces and militants associated with the Islamic State.
The update prohibits flights because of “the potentially hazardous situation created by the armed conflict”.
The FAA said the prohibition will not be reviewed until at least the end of the year.
Flight warnings gained greater attention after Malaysia Airlines Flight 17 was shot down July 17th.
The aircraft came down over Ukraine, where pro-Russia separatists are fighting government forces.
The FAA also suspended US flights to Israel for 36 hours on July 22nd, when a rocket fell near the airport in Tel Aviv.