Three countries — Ethiopia, China and Indonesia — grounded all Boeing 737 Max 8 jets on Monday, a day after 157 people were killed when an Ethiopian Airline flight bound for Kenya crashed shortly after takeoff in Addis Ababa.
The jet was the same make and model as the plane that crashed off Indonesia last year, killing all 189 people aboard.
Ethiopian Airlines said its move to ground its Max 8 jets was intended as an "extra safety precaution." It also announced Monday that the aircraft's black boxes — the flight data and cockpit voice recorders — had been recovered.
Chinese aviation authorities said they had suspended operations of all Max 8 jets on Monday "in line with the management principle of zero tolerance for safety hazards and strict control of safety risks."
CNBC reported that Chinese airlines operate 96 of the aircraft; Boeing records indicate that Ethiopian Airlines flies four others, part of an order of 30 by the airline.
Chinese authorities noted several similarities between the crash on Sunday and that of Lion Air Flight JT610 in Indonesia in late October: They involved the same model of aircraft, each of which had been recently delivered, and both occurred within minutes of takeoff.
The Associated Press reported Monday that Indonesia grounded its Max 8 jets for inspections after Sunday's crash.
Cayman Airways, which flies to the U.S. and countries in the Caribbean, also said that it will suspend operations of both of its 737 Max 8 jets "until more information is received."
Other aviation officials and experts cautioned against rushing to link the crashes, however, saying it was too early to draw any conclusions.
Officials lost contact with Flight 302, a Boeing 737 Max 8 jetliner flying from Addis Ababa, the Ethiopian capital, to Nairobi, the Kenyan capital, at 8:44 a.m. (1:44 a.m. ET), authorities said.
That was about six minutes after the plane took off from Bole International Airport, they said. Tewolde Gebremariam, the airline's chief executive, said that the captain reported "difficulties" and asked to return to the airport but that the plane then "was lost from the radar — it disappeared."
The Ethiopian Airlines jet had been in service for only four months and had no known technical issues, Gebremariam said.
"We cannot rule out anything."
Lion Air Flight JT610 was even newer when it crashed into the sea shortly after takeoff from Jakarta, the Indonesian capital, in late October, having been in service for only 2½ months.
Indonesian authorities said that contact with Flight JT610 was lost after 13 minutes and that the captain reported a "flight control problem." Pilots flying the same plane a day earlier had experienced a similar problem, authorities said.
Weather was good on the day of both crashes.
Beyond that, it's inappropriate to draw any comparisons so early in the investigation of Sunday's crash, said Capt. John Cox, an aviation safety management specialist at the University of Southern California who is an aviation analyst for NBC News.
"The Lion Air jet had been experiencing mechanical problems for the four days prior to the accident," said Cox, a former executive air safety chairman for the Air Line Pilots Association International. "Everything we have heard so far is that is not true of the Ethiopian plane."
Gebremariam said the pilot, senior Capt. Yared Getachew, had an excellent record with more than 8,000 hours of flight time.
"It is a brand new airplane with no technical remarks, flown by a senior pilot, and there is no cause that we can attribute at this time," he said at a news conference, adding, "We cannot rule out anything."
Likewise, the International Federation of Air Line Pilots' Associations said it "stresses the need to avoid speculation as to what happened to the aircraft."
The 737 Max 8 is Boeing's successor to the 737-800, one of the workhorses of civil aviation; it has been in commercial service for only 22 months, since the first one was flown by Malindo Air, a subsidiary of Lion Air, in May 2017.
Ethiopian Airlines is well-respected in aviation circles, having been accepted into the Star Alliance — which includes Air Canada, Lufthansa and United Airlines — in 2011.
Should the crashes turn out to have stemmed from similar problems, it would have been despite the efforts of the Boeing Co. and the U.S. Federal Aviation Administration.
In a preliminary report in November, KNKT, Indonesia's transportation safety commission, said the Lion Air jet wasn't airworthy on either of its last two flights.
The commission highlighted the airline's maintenance practices and pilot training, as well as a revised Boeing safety system designed to automatically correct the jet's flight path if data from sensors indicated that the plane was stalling or losing lift.
U.S. pilots and Indonesian investigators said at the time that information about the automated system wasn't covered in the aircraft's flight manual. Boeing responded by issuing a bulletin to make sure airlines trained their pilots in how to shut off the system if it engaged in error.
The FAA likewise ordered all U.S. airlines that use 737 Max aircraft to obey the bulletin.
Boeing and the U.S. National Transportation Safety Board are sending teams to Ethiopia to assist with the new investigation.
Cox said that because of the interest in the crash, "we'll know fairly quickly" what happened.
"It's all in the data-gathering mode at this point," he said. "Everybody wants to know what happened, but it's too early in the process to provide an answer to that question. It's more important to be accurate than to be quick."