0450 GMT March 22, 2019
The still unexplained crash, which happened just after take-off from Addis Ababa, followed another disaster involving a Boeing 737 MAX in Indonesia five months ago that killed 189 people. Though there is no proof of links, the twin disasters have spooked passengers, led to the grounding of most of Boeing's 737 MAX fleet and hammered shares in the world's biggest plane maker, Reuters reported.
Since the Indonesia crash, there has been attention on an automated anti-stall system that dips the aircraft's nose down.
Ethiopia Airlines spokesman Asrat Begashaw said it was still unclear what happened on Sunday, but its pilot had reported control issues – as opposed to external factors such as birds.
"The pilot reported flight control problems and requested to turn back. In fact he was allowed to turn back," he said.
A decision where in Europe to send the black boxes would be taken by Thursday, the airline said.
Multiple nations, including the European Union, have suspended the 737 MAX, grounding about two-thirds of the 371 jets of that make in operation around the world, according to Reuters calculations.
Many airlines were managing to keep to schedule by using other jets while economic woes meant some may be grateful for a pause. The biggest impact could be on future deliveries given Boeing has nearly 5,000 more 737 MAXs on order.
India said it would not take any deliveries until safety concerns were cleared and Ethiopian Airlines said it would decide whether to cancel orders after a preliminary probe.
Passengers were fretting too, with many seeking reassurances they would not be flying on a 737 MAX. Kayak.com was the first big site to say it would modify filters to allow customers to exclude particular types of planes from queries.
Nevertheless, the United States held out against suspension and Boeing affirmed its "full confidence" in the model.
Boeing shares have fallen some 11 percent since the crash, losing $26.65 billion of market value.
More than a dozen relatives of those who perished paid their respects on Wednesday at the rural site where Flight ET 302 came down in a fireball. Workers set up tents decorated with white roses.
Given problems of identification of charred remains, it will take days to start returning them to families, probably weeks for some which will require dental or DNA testing.
The victims came from more than 30 nations.
Of the top 10 nations by air passenger travel, all but the United States and Japan halted the 737 MAX. Egypt, Thailand, Lebanon, Serbia, Kosovo and Uzbekistan joined them on Wednesday.
Resisting pressure, the US Federal Aviation Administration's (FAA) acting administrator Dan Elwel said its review had shown "no systemic performance issues."
The three US airlines using the 737 MAX – Southwest Airlines Co, American Airlines Group Inc and United Airlines – stood by the aircraft.