The US aviation agency has barred all civil aircraft from flying in Iranian airspace above the Strait of Hormuz and the Gulf of Oman, noting that “numerous” planes were in the area when a US drone was shot down.

The US Federal Aviation Administration (FAA) claims the nearest civil aircraft was flying 45 nautical miles (51 miles) from the US Navy high-altitude drone.

New...FAA issues no-fly zone order in Persian Gulf and Gulf of Oman for U.S. interests pic.twitter.com/UPkriGRRfX — Ethan Klapper (@ethanklapper) June 21, 2019

The agency said it is worried by the ongoing tensions and increased military activity in an area with heavy civil air traffic.

The ban will mostly affect flights going from North America to Asia eastwards.

Earlier Thursday, US carrier United Airlines canceled all flights from Newark International Airport in New Jersey to Chhatrapati Shivaji Maharaj International Airport (BOM), India’s primary international airport in Mumbai. The Chicago-based company cited “a thorough safety and security review of our India service through Iranian airspace.”

Earlier, two other major US carriers, American Airlines and Delta Air Lines, said they did not fly over Iranian airspace.

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The ban comes after Iran’s air defenses shot down a high-altitude US Navy drone on Thursday morning. While Iran insists that the drone was moving in stealth mode over its territorial waters, the US argues that it was flying over international waters. The incident has further strained an already tense situation in the region, with Washington not ruling out an air strike against Iran in retaliation to the incident.

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The flare-up between the US and Iran is not the only geopolitical row to affect United's India services. Earlier this year, it suspended flights between Newark and New Delhi until early July amid the standoff between India and Pakistan that saw their fighter jets engage in an aerial dogfight over the border. In the wake of the incident, Pakistan closed its airspace for India.