The US was one of the last countries to shut down the Boeing model after two deadly downings in six months, dozens of nations had made the move soon after the Ethiopia disaster.
Meanwhile, Boeing – facing its worst crisis in years – recommended a temporary suspension of the “entire global fleet” of the 737 MAX aircraft on Wednesday.
“We are supporting this proactive step out of an abundance of caution,” said Dennis Muilenburg, Boeing’s president, CEO and chairman in a statement on the company’s website.
“We are doing everything we can to understand the cause of the accidents in partnership with the investigators, deploy safety enhancements and help ensure this does not happen again.”
The US Federal Aviation Administration (FAA) ordered the temporary grounding of all 737 MAX aircraft operated by US airlines or in US airspace.
It said the decision was based on new evidence gathered at the Ethiopia Airlines crash site, near the capital Addis Ababa, as well as “newly refined satellite data”.
“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.
The grounding was welcomed by aviation workers in the US.
John Samuelsen, international president of the Transport Workers Union of America, which represents aviation workers and flight attendants, said the grounding of the fleet was right “both for air travellers and aviation workers”.
The FAA’s move came minutes after US President Donald Trump issued an emergency order for the grounding of all Boeing 737 MAX 8 and MAX 9 aircraft in the country.
“I didn’t want to take any chances,” said Trump. “We could have delayed it. We maybe didn’t have to make it at all. But I felt it was important both psychologically and in a lot of other ways.
“The safety of the American people, of all people, is our paramount concern.”
Sunday’s Ethiopian Airlines crash was the second accident involving the US-based aerospace giant’s MAX 8 model within six months.
Last October, a Lion Air-operated MAX 8 went down in Indonesia, killing 189 people.
Both crashes took place shortly after takeoff and have prompted intense scrutiny of the plane’s control systems.
New information from the wreckage in Ethiopia and newly refined data about the plane’s flight path indicated some similarities between the two disasters “that warrant further investigation of the possibility of a shared cause”, the FAA statement said.
Acting administrator of the FAA, Daniel Elwell, said he did not know how long the US grounding of the aircraft would last. A software fix for the 737 MAX that Boeing has been working on since the Indonesia crash will take months to complete, Elwell told reporters.
Dozens of nations banned the use of 737 MAX models in their airspace immediately after the Ethiopia crash, but for days the US continued to say that was unneccesary.
American lawmakers are now questioning why it took so long for the Trump administration and the FAA to take similar action.
Shares in Boeing fell precipitously on Wednesday, plunging by nearly three percent and putting the stock down more than 13 percent since before Sunday’s crash.
The downturn has wiped billions off the company’s market value.
The single-aisle 737 is central to Boeing’s future in its battle with European rival Airbus SE. The new variant of the 737, the fastest-selling jetliner in Boeing’s history, is viewed as the likely workhorse for global airlines for decades.