He called it "an emergency order of prohibition."
The FAA followed up with a formal order, saying it "made this decision as a result of the data gathering process and new evidence collected at the site and analyzed today." The agency said the grounding will remain in effect "pending further investigation."
Boeing said in a statement that the company "continues to have full confidence in the safety of the 737 MAX" but will "recommend to the FAA the temporary suspension of operations of the entire global fleet of 371 737 MAX aircraft."
"We are supporting this proactive step out of an abundance of caution. Safety is a core value at Boeing for as long as we have been building airplanes and it always will be. There is no greater priority for our company and our industry. 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," Boeing CEO Dennis Muilenburg said.
The new plane crashed in clear weather six minutes after taking off from Addis Ababa for Nairobi on Sunday.
Ethiopian Airlines said the senior pilot issued a distress call and was told to return but all contact was lost shortly afterward. The plane plowed into the ground at Hejere near Bishoftu, scattering debris like a shredded book, a battered passport and business cards in multiple languages.
"I heard this big noise," resident Tsegaye Reta told the AP. "The villagers said that it was a plane crash, and we rushed to the site. There was a huge smoke that we couldn't even see the plane. The parts of the plane were falling apart."
One witness has told The Associated Press that smoke was coming from the plane's rear before it crashed in a rural field. "The plane rotated two times in the air, and it had some smoke coming from the back then, it hit the ground and exploded," Tamrat Abera said.
Pope Francis sent his condolences to the families of the victims of the plane crash in Ethiopia.
Cardinal Pietro Parolin, the Vatican's secretary of state, said in a statement Monday that the pope was sad to learn about the crash and "offers prayers for the deceased from various countries and commends their souls to the mercy of Almighty God."
The statement said, "Pope Francis sends heartfelt condolences to their families, and upon all who mourn this tragic loss he invokes the divine blessings of consolation and strength."
As a growing global team searched for answers, a woman stood near the crash site Tuesday morning, wailing.
Kebebew Legess said she was the mother of a young Ethiopian Airlines crew member among the dead.
"She would have been 25 years old but God would not allow her," she wept. "My daughter, my little one."
RELATED: What we know about the victims of the Ethiopia crash
People from 35 countries died in the crash. It should take five days to identify the victims' remains, Ethiopian Airlines spokesman Asrat Begashaw told the AP.
Among the vicitms already identified are a writer from New Jersey and California, and an army captain from Illinois.
Kenya lost 32 people, more than any country. Relatives of 25 of the victims had been contacted, Macharia said, and taking care of their welfare was of utmost importance.
"Some of them, as you know, they are very distressed," he said. "They are in shock like we are. They are grieving."
In Addis Ababa, members of an association of Ethiopian airline pilots cried uncontrollably for their dead colleagues. Framed photos of seven crew members sat in chairs at the front of a crowded room.
Canada, Ethiopia, the U.S., China, Italy, France, Britain, Egypt, Germany, India and Slovakia all lost four or more citizens.
At least 21 staff members from the United Nations were killed in the crash, said U.N. Secretary-General Antonio Guterres, who led a moment of silence at a meeting where he said "a global tragedy has hit close to home."
Both Addis Ababa and Nairobi are major hubs for humanitarian workers, and some had been on their way to a large U.N. environmental conference set to begin Monday in Nairobi. The U.N. flag at the event flew at half-staff.
An Ethiopian Airlines spokesman confirmed on Wednesday that the plane's black box will be sent to Europe.
Asrat Begashaw has declined to tell The Associated Press which country will be analyzing the voice and data recorders of the flight.
After the plane's flight data and cockpit voice recorders were found, an airline said one of the recorders was partially damaged and "we will see what we can retrieve from it." The official spoke on condition of anonymity for lack of authorization to speak to the media.
The Federal Aviation Administration arrived at the crash site with representatives from the National Transportation Safety Board on Tuesday, joining the global investigation.
As Ethiopia observed a day of mourning on Monday, Red Cross workers slowly picked through the widely scattered debris near the blackened crash crater, looking for the remains of the dead, while heavy machinery dug for larger pieces of the plane.
Accident Bulletin no. 6— Ethiopian Airlines (@flyethiopian) March 11, 2019
Issued on March 11, 2019 at 01:40 PM Local Time
The Digital Flight Data Recorder(DFDR) and Cockpit Voice Recorder(CVR) of ET302 have been Recovered.
Ethiopian authorities are leading the investigation into the crash, assisted by the U.S., Kenya and others.
"These kinds of things take time," Kenya's Transport Minister James Macharia told reporters.
The head of Indonesia's national transport safety agency, Soerjanto Thahjono, offered to aid the Ethiopian investigation into Sunday's crash.
Alan Diehl, a former National Transportation Safety Board investigator, said reports of large variations in vertical speed during the Ethiopian jetliner's ascent were "clearly suggesting a potential controllability problem."
Other possible causes include engine problems, pilot error, weight load, sabotage or bird strikes, he said.
Grounding flights around the world
On Wednesday, the United States became the last major player to ground the newer models of the Boeing 737 Max.
President Donald Trump said any plane currently in the air will go to its destination and then be grounded, adding that pilots and airlines have been notified.
He said the safety of the American people is of "paramount concern."
Before the grounding in the U.S., Peter Goelz, a former managing director for the U.S. National Transportation Safety Board who now is an aviation consultant, told the Associated Press that that the Federal Aviation Administration was facing mounting pressure to follow suit with the growing list of countries and airlines that had grounded the planes.
"They are the last remaining significant regulatory authority that has not pulled the plug on this aircraft," Goelz said. "They are outliers. It's putting a lot of pressure on them, I'm sure."
Earlier Wednesday, Canadian Transport Minister Marc Garneau said new information they received Wednesday morning in the form of satellite data shows a possible but unproven similarity to a previous Max 8 crash.
Germany, France, Ireland and Turkish Airlines joined the list on Tuesday.
The UK Civil Aviation Authority said in a statement earlier Tuesday that though it had been monitoring the situation, it had as a precautionary measure "issued instructions to stop any commercial passenger flights from any operator arriving, departing or overflying UK airspace."
More airlines had already announced they would ground the jets. An official with South Korean airline Eastar Jet said they were doing so in response to customer concerns.
Airlines in China and Indonesia, Aeromexico, Brazil's Gol Airlines, India's Jet Airways and others also temporarily grounded their Max 8s.
Australia suspended all flights into or out of the country by Boeing 737 Max aircraft.
Boeing said it did not intend to issue any new recommendations about the aircraft to its customers. It was sending a technical team to the crash site to help the investigators.
Earlier in the week, as several international airlines grounded their Boeing 737 Max 8s, American and Southwest Airlines continue to use them.
"We have full confidence in the aircraft and our crew members," American said in their statement on the matter.
"We remain confident in the safety and airworthiness of our entire fleet," Southwest said in a statement. The airline also said its customers with concerns about their aircraft contact customer service.
But others in the U.S. began pressing for action.
The Association of Professional Flight Attendants, which represents more than 26,000 flight attendants at American Airlines, called on CEO Doug Parker to "strongly consider grounding these planes until an investigation can be performed."
DePaul University Professor Joe Schwieterman said there will likely be some change ahead for airlines that operate these planes.
"There is such a big loss of life we have to assume this is going to require some technological fix," Schwieterman said.
Two pilots opearting the aircraft in the U.S. reported to authorities in November that the nose of their plane suddenly dipped after engaging the autopilot, ABC News reports.
The FAA says there are no verfied incidents in the U.S. similar to the first crash, and that there is no basis to order grounding the plane, according to ABC News. The FAA said its decision is based on the evidence, which makes the findings of the investigation into the second crash critical.
737 Max 8
In a new statement on Tuesday, Boeing reiterarated that it was not issuing new guidance:
Safety is Boeing's number one priority and we have full confidence in the safety of the MAX. We understand that regulatory agencies and customers have made decisions that they believe are most appropriate for their home markets. We'll continue to engage with all of them to ensure they have all the information they need to have the confidence they need safely continue to operate their fleets or return them to service. It is also important to note that the Federal Aviation Administration is not mandating any further action at this time, and based on the information currently available, we do not have any basis to issue new guidance to operators.
The 737 is the best-selling airliner in history, and the Max, the newest version of it with more fuel-efficient engines, is a central part of Boeing's strategy to compete with European rival Airbus.
Boeing has delivered about 350 737 Max planes to scores of airlines and has orders for more than 5,000.
Sunday's crash was strikingly similar to that of a Lion Air jet of the same Boeing model in Indonesian seas last year, killing 189 people. The crash was likely to renew questions about the 737 Max 8, the newest version of Boeing's popular single-aisle airliner, which was first introduced in 1967 and has become the world's most common passenger jet.
RELATED: Boeing stocks tumble day after Ethiopia crash
Like the Ethiopian Airlines crash, which happened minutes after the jet's takeoff from Addis Ababa, the Lion Air jet that crashed off Indonesia had erratic speed during the few minutes it was in the air.
Safety experts cautioned, however, against drawing too many parallels between the two disasters.
"I do hope though that people will wait for the first results of the investigation instead of jumping to conclusions based on the very little facts that we know so far," said Harro Ranter, founder of the Aviation Safety Network, which compiles information about accidents worldwide.
The situation will be better understood after investigators analyze the Ethiopian plane's black boxes, said William Waldock, an aviation-safety professor at Embry-Riddle Aeronautical University.
Waldock said the way the planes both crashed - a fatal nosedive - was likely to raise suspicion. Boeing will likely look more closely at the flight-management system and automation on the Max, he said.
"Investigators are not big believers in coincidence," he said.
Chicago-based Boeing said it did not intend to issue any new guidance to its customers. It plans to send a technical team to the crash site to help investigators and issued a statement saying it was "deeply saddened to learn of the passing of the passengers and crew" on the jetliner.
The crash shattered more than two years of relative calm in African skies, where travel had long been chaotic. It also was a serious blow to the Ethiopian Airlines, which has expanded to become the continent's largest and best-managed carrier and turned Addis Ababa into the gateway to Africa.
The state-owned carrier has a good reputation and the company's CEO told reporters no problems were seen before Sunday's fight. But investigators also will look into the plane's maintenance, which may have been an issue in the Lion Air crash.
The plane was delivered to Ethiopian Airlines in November. The jet's last maintenance was on Feb. 4, and it had flown just 1,200 hours.
Days after the Indonesian accident, Boeing notified airlines that faulty information from a sensor could cause the plane to automatically point the nose down. The automated system kicks in if sensors indicate that a plane is about to lose lift, or go into an aerodynamic stall. Gaining speed by diving can prevent a stall.
The notice reminded pilots of the procedure for handling such a situation, which is to disable the system causing the automatic nose-down movements.
Indonesian investigators are examining whether faulty readings from a sensor might have triggered the automatic nose-down command to the plane, which the Lion Air pilots fought unsuccessfully to overcome.
The Lion Air plane's flight data recorder showed problems with an airspeed indicator on at least four previous flights, although the airline initially said the problem was fixed.
Boeing Chairman and CEO Dennis Muilenburg said in December that the Max is a safe plane.
In his first comments about the tragedy, President Donald Trump focused on the complexity of operating aircraft.
Airplanes are becoming far too complex to fly. Pilots are no longer needed, but rather computer scientists from MIT. I see it all the time in many products. Always seeking to go one unnecessary step further, when often old and simpler is far better. Split second decisions are....— Donald J. Trump (@realDonaldTrump) March 12, 2019
....needed, and the complexity creates danger. All of this for great cost yet very little gain. I don’t know about you, but I don’t want Albert Einstein to be my pilot. I want great flying professionals that are allowed to easily and quickly take control of a plane!— Donald J. Trump (@realDonaldTrump) March 12, 2019
The ABC Owned Stations and ABC News contributed to this report.