The order came after United Airlines suspended flights between New Jersey's Newark airport and Mumbai.

Washington on Thursday barred American civilian flights from Tehran-controlled airspace over the Gulf and Gulf of Oman "until further notice" after Iran shot down a US military drone.

The restrictions are due to "heightened military activities and increased political tensions in the region, which present an inadvertent risk to US civil aviation operations and potential for miscalculation or misidentification," the US Federal Aviation Administration said.

"The risk to US civil aviation is demonstrated by the Iranian surface-to-air missile shoot-down of a US unmanned aircraft system," according to the aviation regulator.