China’s civilian aviation authority ordered all Chinese airlines to ground their Boeing 737 Max 8 planes indefinitely on Monday after one of the aircraft crashed in Ethiopia.

The Civil Aviation Administration of China said the order is to take effect by 6 p.m. (1000 GMT) Monday. It said the order, issued Monday morning, was “taken in line with the management principle of zero tolerance for security risks,” because the crash was the second after another of the planes fell into the ocean off the coast of Indonesia in similar circumstances on Oct. 29, killing all aboard. The head of Indonesia’s national transport safety agency, Soerjanto Thahjono, offered Monday to assist the Ethiopian investigation into Sunday’s crash.Like the Ethiopian Airlines crash, which happened minutes after the jet’s takeoff from Addis Ababa and killed all 157 people on board, the Lion Air jet that crashed off Indonesia had erratic speed in the few minutes it was in the air.

The crash put global aviation authorities on alert. Cayman Airways says it was temporarily grounding the two Boeing 737 Max 8 aircraft it operates, as of Monday. The president and CEO of the Caribbean carrier, Fabian Whorms, acknowledged the cause of the Ethiopian crash was unclear, but said the airline was taking the step because of its “commitment to putting the safety of our passengers and crew first.” China’s aviation authority said it would issue further notices after consulting with the U.S. Federal Aviation Administration and Boeing. Eight Chinese nationals on board the Ethiopian Airlines flight that crashed. The crash in Ethiopia has renewed safety questions about the newest version of Boeing’s popular 737 airliner, since the plane was new and the weather was clear at the time. The pilots tried to return to the airport but never made it. But safety experts cautioned against quickly drawing too many parallels between the two crashes.

It is very early, and more will be known after investigators find and analyze the Ethiopian plane’s black boxes, said William Waldock, an aviation-safety professor at Embry-Riddle Aeronautical University. But suspicion will be raised because the same type of plane appeared to crash the same way — a fatal nosedive that left wreckage in tiny pieces. “Investigators are not big believers in coincidence,” he said. Waldock said Boeing will look more closely at the flight-management system and automation on the Max.

Boeing representatives did not immediately respond for comment. The company tweeted that it was “deeply saddened to learn of the passing of the passengers and crew” on the Ethiopian Airlines Max airplane. The Chicago-based company said it would send a technical team to the crash site to help Ethiopian and U.S. investigators.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 and has orders for more than 5,000. It is already in use by many airlines including American, United and Southwest.

Alan Diehl, a former National Transportation Safety Board investigator, said the similarities in the crashes included both crews encountering a problem shortly after takeoff, and reports of large variations in vertical speed during the Ethiopian jetliner’s ascent, “clearly suggesting a potential controllability problem.” But there are many possible explanations, including engine problems, pilot error, weight load, sabotage or bird strikes, he said. Ethiopian has a good reputation, but investigators will look into the plane’s maintenance, especially since that may have been an issue in the Lion Air crash. Ethiopian Airlines’ CEO told reporters a maintenance check-up did not find any problems with the plane before Sunday’s flight, “so it is hard to see any parallels with the Lion Air crash yet,” said Harro Ranter, founder of the Aviation Safety Network, which compiles information about accidents worldwide. “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,” he said. The NTSB said it was sending a team of four to assist Ethiopian authorities. Boeing and the U.S. investigative agency are also involved in the Lion Air probe. Indonesian investigators have not stated a cause for that crash, but they are examining whether faulty readings from a sensor might have triggered an automatic nose-down command to the plane, which the Lion Air pilots fought unsuccessfully to overcome. 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 Lion Air plane’s flight data recorder showed problems with an airspeed indicator on four flights, although the airline initially said the problem was fixed. The director general of Air Transportation in Indonesia, Polana B. Pramesti, said the agency has been following up on an FAA airworthiness directive and is still evaluating the 737 Max 8 following the crash. Days after the Oct. 29 accident, Boeing sent a notice to airlines that faulty information from a sensor could cause the plane to automatically point the nose down. The notice reminded pilots of the procedure for handling such a situation, which is to disable the system causing the automatic nose-down movements.

Boeing Chairman and CEO Dennis Muilenburg said in December that the Max is a safe plane, and that Boeing did not withhold operating details from airlines and pilots. Pilots at some airlines, however, including American and Southwest, have protested that they were not fully informed about the new system. The Lion Air incident appears not to have harmed Boeing’s ability to sell the Max. Boeing’s stock fell nearly 7 percent on the day of the Lion Air crash. Since then it has soared 26 percent higher, compared with a 4 percent gain in the Standard & Poor’s 500 index.