Some of the world's leading carriers including British Airways, Qantas and Singapore Airlines on Friday suspended flights over the Strait of Hormuz, as Iran-US tensions flare over the downing of a drone. The suspensions will affect many thousands of passengers and came after the Federal Aviation Administ-ration in the United States issued a Notice to Airmen (NOTAM), "prohibiting US-registered aircraft from operating over the Persian Gulf and Gulf of Oman". The NOTAM was in response to "heightened military activities and increased political tensions that might place commercial flights at risk", an FAA statement said, as Tehran and Washington engaged in a war of words over Thursday's missile strike on the drone.
The FAA's notice applies only to US-registered airlines, and United Airlines said it was suspending its Newark-Mumbai service in response. But European and Asian operators were taking no chances.
"Our safety and security team are constantly liaising with authorities - including the likes of the FAA - around the world as part of their comprehensive risk assessment into every route we operate," a BA spokeswoman said.
Germany's Lufthansa and Dutch airline KLM followed suit in bypassing the Hormuz area, although Air France said it was already flying further south. Dubai-based Emirates said it had rerouted flights to avoid "areas of possible conflict".
Iran's downing of the drone - which Washington insists was above international waters but Iran says was within its airspace - has seen tensions between the two countries spike further after a series of attacks on tanker ships blamed by the US on Tehran.
The Global Hawk surveillance aircraft can attain a maximum altitude of 60,000 feet (18.3 kilometres), nearly double the typical cruising height of a passenger plane.
KLM said: "The incident with the drone is reason not to fly over the Strait of Hormuz for the time being. This is a precautionary measure."
The Netherlands is still reeling from the downing of Malaysia Airlines flight MH17 in 2014, which was hit a missile over eastern Ukraine's Donetsk region where pro-Russian separatist rebels are battling Ukraine government forces.
All 298 people on board were killed, 196 of them Dutch.
International investigators on Wednesday charged three Russians and a Ukrainian with murder over the shooting down of the plane, which was travelling between Amsterdam and Kuala Lumpur.
The incident forced airlines on the busy Europe-Asia route to divert flights away from Ukraine airspace.
Responding to the latest tensions over Iran, Malaysia Airlines said it "is closely monitoring the situation and is guided by various assessments including security reports and NOTAMs by respective airspace control authorities".
Australia's flag carrier Qantas said it too was avoiding the Strait of Hormuz and Gulf of Oman "until further notice", while Singapore Airlines warned passengers that its flight times to Europe would likely take longer now.
Europe-Asia flights have already faced disruption since February, when Pakistan restricted large swathes of airspace near India due to cross-border air strikes which came close to all-out war between the nuclear-armed rivals.
"This (Pakistan's action) has also pushed much of the transiting traffic south, nearer to the area now prohibited to US carriers," the flight-tracking website Flightradar24 said in a blog.
Alex Macheras, an independent aviation analyst in London, said the Hormuz diversions were another image problem for Iran after the "mass exodus" of European airlines, which had to abandon their Tehran routes following the restoration of US sanctions.
Pointing back to the Ukraine downing, Pakistan's closure and other incidents, he told AFP that "more and more passengers have been affected by geopolitics", and that many travellers were avoiding stopovers in the Middle East altogether.