The US Federal Aviation Administration (FAA) has ordered US carriers to avoid operating in airspace over Iraq and Iran.
The directive comes after Iran launched missile strikes on two Iraqi military bases hosting US personnel on Wednesday (8 January).
Carriers have also been told by the FAA to avoid flying over the Gulf of Oman and waters between Iran and Saudi Arabia.
The missile attacks represent Iran’s first major act of retribution after top Iranian general Qasem Soleimani was killed in a US airstrike on Friday (3 January).
There is no indication at this stage whether the strikes resulted in any casualties at the two Iraqi bases.
US president Donald Trump tweeted he would make a statement on Wednesday morning, adding: "all is well. Assessment of casualties and damages taking place now."