Baghdad's airspace was temporarily "restricted" on Tuesday morning for about an hour because of the threat of rocket or mortar attack, a US military spokeswoman said.
"We learned that there was a credible indirect fire threat earlier today, which resulted in an elevation in security level and additional security measures enacted, but the airport was not shut down," Major Angela Funaro told AFP in an emailed response to questions.
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Indirect fire is the term the US military uses to refer to rocket or mortar attacks.
Funaro said a "temporary flight restriction" was imposed on Baghdad for around an hour, but did not give further details and declined to say what security measures were enacted.
Baghdad airport is west of the city and adjacent to Victory Base, one of the largest US military installations in Iraq.
The US is currently responsible for securing Iraq's airspace, but all American forces are due to withdraw by year's end, unless Baghdad and Washington reach an accord on a post-2011 training mission.