The United States has joined other nations in grounding Boeing 737 Max 8 and Max 9 jets, citing new satellite data and evidence from the scene of Sunday's crash of an Ethiopian Airlines plane that killed all 157 on board.
It was the second time the US Federal Aviation Administration (FAA) has halted flights of a Boeing plane in six years, grounding the 787 Dreamliner in 2013 due to problems with smoking batteries.
"The agency made this decision as a result of the data gathering process and new evidence collected at the site and analysed today," the FAA said in a statement, shortly after US President Donald Trump announced the planes would be grounded.
"This evidence, together with newly refined satellite data available to FAA this morning, led to this decision," the FAA said, adding that the grounding will remain in effect as the FAA investigates.
Shares of the world's biggest plane maker, which were up earlier in the session, fell 2 per cent to $US370.48. The shares have fallen about 13 per cent since Sunday's crash, losing about $US32 billion of market value.
Boeing, which maintained that its planes were safe to fly, said it supported the move to temporarily ground 737 MAX flights.
The United States joins Europe, China and other countries in grounding Boeing's newest plane since the Ethiopian Airlines flight crashed soon after taking off from Addis Ababa.
The still-unexplained crash followed another involving a Boeing 737 MAX in Indonesia five months ago that killed 189 people. Although there is no proof of any link, the two disasters have spooked passengers.
The grounding was welcomed by air workers in the United States.
"He (Trump) did the right thing by grounding this fleet, both for air travellers and aviation workers," John Samuelsen, international president of the Transport Workers Union of America.
"Our members are excited, and are no longer concerned about stepping into a workplace which could lead to the end of their lives, potentially."
Canada also grounded 737 MAX jets on Wednesday, saying satellite data suggested similarities to the previous crash involving the same plane model in October.
US-based aircraft-tracking firm Aireon provided the satellite data to the FAA, Transport Canada and several other authorities, company spokeswoman Jessie Hillenbrand said.
Aireon's space-based system can monitor data from aircraft equipped with Automatic Dependent Surveillance-Broadcast (ADS-B) transponders. The data is considered less detailed than that in black boxes, which look at systems running inside the plane.
Earlier on Wednesday, Germany's federal agency responsible for investigating air accidents said it would not analyse the black box from the Ethiopian Airlines plane, casting uncertainty over the process of finding out what may have caused the disaster. The US FAA said the black boxes were headed to France later on Wednesday.
Ethiopian 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.
