The EU closed its airspace to Boeing 737 MAX planes on Tuesday, joining similar action by nations across the globe following a second deadly accident in just five months.
Fleets of the best-selling workhorse plane were also grounded by airlines as safety concerns swirled, sending Boeing shares tumbling another seven percent in Tuesday trading and wiping billions more off its market value.
On Sunday, a new Ethiopian Airlines 737 MAX 8 went down minutes into a flight from Addis Ababa to Nairobi, killing all 157 people on board.
In October, a Lion Air jet of the same model crashed in Indonesia, killing 189 people shortly after takeoff from Jakarta.
The widening airspace closures puts pressure on Boeing, the world's biggest planemaker, to prove the MAX planes are safe.
The full extent of the impact on international travel routes was unclear, although there are some 350 MAX 8 planes currently in service around the world with more than 5,000 on order.
The EU aviation safety agency said it was closing European airspace to all MAX aircraft currently operating.
It noted that the "exact causes" of the Lion Air crash were still being investigated.
"Since that action, another fatal accident occurred," EASA said, referring to Sunday's Ethiopian Airlines disaster.
"At this early stage of the investigation, it cannot be excluded that similar causes may have contributed to both events," the agency said.
India late Tuesday joined the list of countries to close its airspace to the jet, a day after saying it had imposed additional interim safety requirements for ground engineers and crew for the aircraft.
Elsewhere, Turkish Airlines, one of the largest carriers in the world, said it was suspending its 12 MAX aircraft from Wednesday, until "uncertainty" was clarified.
Low-cost airline Norwegian Air Shuttle, South Korea's Eastar Jet and South Africa's Comair also said they would halt flights.
On Twitter, US President Donald Trump weighed in on the situation, writing: "Airplanes are becoming far too complex to fly."
"Pilot are no longer needed, but rather computer scientists from MIT," he wrote, referring to the prestigious university in Massachusetts.
US carriers have so far appeared to maintain confidence in Boeing, which has said it is certain the planes are safe to fly.
The US federal aviation authority, the FAA, has not grounded the MAX but ordered the manufacturer to make design changes.
The move was not enough to reassure the UK Civil Aviation Authority, which said it was banning the planes from UK airspace "as a precautionary measure".
Global air travel hub Singapore, as well as Australia, Malaysia and Oman were among the other countries to ban all MAX planes from their airspace.
China, a hugely important market for Boeing, had already ordered domestic airlines to suspend operations of the plane on Monday, as did Indonesia.
Argentina's flag carrier also grounded five MAX 8 aircraft on Tuesday, as did airlines in countries including Brazil and Mexico.
'Significant industry impact'
Boeing has described the MAX series as its fastest-selling family of planes, with more than 5,000 orders placed to date from about 100 customers.
But not since the 1970s -- when the McDonnell Douglas DC-10 suffered successive fatal incidents -- has a new model been involved in two deadly accidents in such a short period.
"I think the impact for the industry is significant," said Gerry Soejatman, a Jakarta-based aviation analyst.
"We have a new type of aircraft -- that type of aircraft has only been in service for two years -- and... we have two accidents with seemingly similar circumstances."
The plane involved in Sunday's crash was less than four months old, with Ethiopian Airlines saying it was delivered on November 15.
It went down near the village of Tulu Fara, some 40 miles (60 kilometres) east of Addis Ababa.
Ethiopian Airlines said the pilot was given clearance to turn around after indicating problems shortly before the plane disappeared from radar.
Its chief executive Tewolde GebreMariam said the plane had flown in from Johannesburg on Sunday, spent three hours in Addis and was "dispatched with no remark", meaning no problems were flagged.
Investigators have recovered the black box flight recorders, which could potentially provide information about what happened, depending on their condition.
The crash cast a pall over a gathering of the UN Environment Programme in Nairobi -- at least 22 staff from several UN agencies were on board the doomed flight.
Kenya had the highest death toll among the nationalities on the flight with 32, according to Ethiopian Airlines.
There were also passengers from Canada, Ethiopia, Italy, the United States, Britain and France.