Grieving families on Wednesday visited the site of the Ethiopian Airlines crash that killed 157 people, as the airline said it would send the black boxes from the plane to France for analysis.
And Ethiopian Airlines chief executive Tewolde Gebremariam said the pilots told air-traffic control that they were having problems controlling the plane before the crash.
The ban on the Boeing 737 Max aircraft became worldwide late on Wednesday after US President Donald Trump joined Canada and other countries in grounding the aircraft amid mounting global fears for the jets' airworthiness.
US authorities said new evidence showed similarities between Sunday's deadly crash and a fatal accident in Indonesia in October.
Distraught relatives of those who died carried pictures of their loved ones as they visited the site, 62 kilometres south-east of Addis Ababa.
They laid wreaths of blooming yellow roses and held each other as they wept in the arid farmland where the plane crashed.
Two black boxes were recovered from the crash site on Monday, one holding voice recordings and other digital data.
Mr Gebremariam told CNN the black boxes would be sent to Europe "in the interest of proximity and speed".
Data from the black box will be all-important to investigations into the incident, Saj Ahmad, chief analyst at StrategicAero Research, told The National.
The voice record will have conversations between the cockpit and the control towers, while the data recorder will have details such as the aircraft's speed, height, weight, stresses and performance, Mr Ahmad said.
Two American agencies – the Federal Aviation Authority and National Transport Safety Board – are assisting Ethiopia with the investigation, along with plane maker Boeing.
As the "state of occurrence", Ethiopia will lead the investigation, said Graham Braithwaite, a professor of safety and accident investigation at Cranfield University in the UK.
But Prof Braithwaite said more agencies might join the investigation.
"If there are particular skills that may come from another state or any other agency – for example, a university – then it is appropriate that the investigator in charge can invite them to participate," he said.
Prof Braithwaite said it was not unusual for the black boxes to be sent overseas because some countries did not have the equipment to analyse the data.
"Aircraft accident investigation depends on international collaboration, all with the common goal of improving flight safety," he said.
The Federal Aviation Administration said findings from the crash site near Addis Ababa and "newly refined satellite data" warranted "further investigation of the possibility of a shared cause for the two incidents."
An FAA emergency order grounded 737 MAX 8 and MAX 9 aircraft until further notice.
Mr Trump said at the White House the "safety of the American people and all peoples is our paramount concern".
FAA acting chief Daniel Elwell said the agency has been "working tirelessly" to find the cause of the accident but faced delays because the black box flight data recorders had been damaged.
The new information shows "the track of that airplane was close enough to the track of the Lion Air flight... to warrant the grounding of the airplanes so we could get more information from the black boxes and determine if there's a link between the two, and if there is, find a fix to that link," Mr Elwell said on CNBC.
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The world's Boeing 737 Max 8 fleet
Mr Gebremariam said speculation about the safety of the aircraft was not helpful but there were "questions without answers".
He said there were "very significant similarities" between the Ethiopian Airlines crash and that of Lion Air.
Ethiopian Airlines flight 302 crashed six minutes after taking off on Sunday morning, killing 149 passengers and eight crew from 35 different countries.
The flight, bound for Nairobi, was carrying delegates to a UN conference on the environment in the Kenyan capital.
