Airlines reroute flights to avoid Iranian airspace as tensions rise Iran shot down an unmanned drone on Thursday.

Major airlines across the globe rerouted flights Friday to avoid flying over the Persian Gulf and Gulf of Oman near Iran after that country shot down an unmanned American drone the day before.

The Federal Aviation Administration (FAA) prohibited "all U.S. carriers and commercial operators" from flying over Iranian airspace. The FAA announced the decision, called a notice-to-airman, or NOTAM, alert, late Thursday. The FAA told ABC News approximately 31 flights per week are affected by the notice. The carriers affected include United, UPS, FedEx, Atlas, and Polar Air.

"All flight operations in the overwater area of the Tehran Flight Information Region (FIR) (OIIX) above the Persian Gulf and Gulf of Oman only are prohibited until further notice due to heightened military activities and increased political tensions in the region, which present an inadvertent risk to U.S. civil aviation operations and potential for miscalculation or mis-identification," the FAA said in a press release.

The NOTAM applies to all U.S. air carriers and commercial operators, but does not apply to U.S.-registered planes for foreign carriers.

A number of foreign-based airlines including Emirates, British Airways, Qantas, Lufthansa, KLM, Singapore Airlines, Etihad Airlines, and Qantas have all said they will avoid the area as a precaution.

Etihad, based in the United Arab Emirates (UAE), told ABC News that it consulted "closely with the UAE Civil Aviation Authority to evaluate the US action."

"Safety is paramount to Etihad Airways, and together with the GCAA we have agreed to change a number of the flight paths we operate to and from the Arabian Gulf," a spokesperson for the airline said.

Emirates, also based in the UAE, said as a precautionary measure they are rerouting all flights away from areas of possible conflict.

"The reroutings have minimally affected the arrival and departure timings of some flights," an Emirates spokesperson said. "The safety of our passengers, crew and aircraft is our number one priority and will not be compromised."

Qantas, the flag carrier of Australia, said they are "adjusting their flight paths over the Middle East to avoid the Strait of Hormuz and Gulf of Oman until further notice." The change will impact the routing of Qantas flights between Australia and London, but a Qantas spokesperson said the impact on flying time will be "negligible."

Lufthansa, the largest airline from Germany, told ABC that "in view of the present tensions between Iran and the USA" the airlines of the Lufthansa Group are routing their flights to avoid flying over Iranian airspace, but that customers "should not suffer any inconvenience, since normal flight operations can continue."

OPSGROUP, a company that provides guidance to global airlines, sent an advisory to their members this morning warning them that "the threat of a civil aircraft shoot down in southern Iran is real" and that "misidentification of aircraft is possible."

Sources told ABC News President Donald Trump ordered a military strike on Iran late Thursday, but then reversed course after a plan was already underway.

Trump’s reason for changing course was unclear, but the reversal was against the advice of Secretary of State Mike Pompeo and National Security Adviser John Bolton.