Several global airlines, including Malaysia Airlines (MAS), are re-routing flights to avoid Iran-controlled airspace over the Strait of Hormuz and the Gulf of Oman after the United States aviation regulator barred its carriers from the area until further notice.
Yesterday's emergency order from the Federal Aviation Administration (FAA) came after Iran took down a high-altitude US drone with a surface-to-air missile, sparking concerns about the safety threat to commercial airlines.
The downing of the unarmed Global Hawk drone (photo, above), which can fly at up to 60,000ft (18,300m), was the latest in a series of incidents in the Gulf region, a critical artery for global oil supplies, that included explosive strikes on six oil tankers.
According to flight tracking applications, the FAA said the nearest civil aircraft was within 45 nautical miles of the unmanned aircraft when it was shot down.
"There were numerous civil aviation aircraft operating in the area at the time of the intercept," FAA said.
Hours earlier, the United Airlines suspended flights between Newark and Mumbai following a safety review.
MAS said it was avoiding the airspace, which it had previously used on flights between Kuala Lumpur and London, Jeddah and Medina.
"The airline is closely monitoring the situation and is guided by various assessments, including security reports and notices to airmen," the Malaysian airline added.
Qantas Airways, Singapore Airlines and KLM said they were re-routing flights to avoid the area.
The FAA said it remained concerned about the escalation of tension and military activity in close proximity to high-volume civil aircraft routes as well as Iran's willingness to use long-range missiles in international airspace with little or no warning.
In July 2014, Malaysia Airlines Flight MH17 was shot down by a missile over Ukraine, killing all 298 on board, prompting carriers to take more steps to uncover threats to their planes.
The US ban does not apply to airlines from other countries, but OPSGROUP, which provides guidance to operators, said carriers globally would take it into consideration.
"Since MH17, all countries rely on advice from the US, the United Kingdom, France and Germany to highlight airspace risk," it said.
"The threat of a civil aircraft shootdown in southern Iran is real."
Earlier today, flight tracking website Flightradar24 showed flights of Qatar Airways and Emirates in the area barred to US carriers. The two airlines did not immediately respond to a request for comment outside business hours.
A United spokesman said customers flying from Mumbai to Newark would be booked on alternative flights back to the United States.
"We continue to explore all our options and remain in close contact with relevant government authorities," he added.