Concern that two crashes involving new Boeing 737 MAX 8s in less than five months may be linked has led operators and regulators to ground about a third of the in-service fleet while investigators work to either connect the two accidents or calm fears.

Groundings started less than 24 hours after Ethiopian Airlines flight ET302, a three-month-old 737 MAX 8, crashed six min. after takeoff from Addis Ababa in clear weather March 10.

Operators Ethiopian, Cayman Airways and Royal Air Maroc—as well as regulators Civil Aviation Administration of China (CAAC) and the Indonesian Directorate General of Civil Aviation (DGCA)—said all aircraft under their control would be grounded.

The general message: The ET302 investigation would be monitored and guidance sought from Boeing and FAA, which said late March 11 it was gathering information and would act “immediately” if a safety-of-flight issue was discovered. 

“Ethiopian Airlines has decided to ground all B-737-8 MAX fleet effective yesterday March 10, 2019 until further notice,” the airline said March 11. “Although we don’t yet know the cause of the accident, we had to decide to ground the particular fleet as extra safety precaution.”

China's groundings come via a Civil Aviation Administration of China (CAAC) order issued March 11 “requesting domestic transportation airlines to suspend the commercial operation” of 737 MAX 8s by 18:00. CAAC cited “the management principle of zero tolerance for safety hazards and strict control of safety risks” in making the move, adding that both MAX 8 crashes occurred “in the takeoff phase” and “have certain similarities.”

CAAC said it “will contact the US Federal Aviation Administration (FAA) and Boeing Company to notify the shipping airlines to resume the commercial operation of the Boeing 737-8 aircraft after confirming the relevant measures to effectively ensure flight safety.”

More than 90 737 MAX 8s are in service with Chinese operators, including Air China, China Eastern, China Southern, and Hainan Airlines. 

DGCA said late March 11 said 737 MAX 8s operated by Indonesian airlines would be grounded while additional inspections are carried out. Inspections are to begin as soon as March 12, the DGCA said. Two Indonesian carriers operate 737 MAX 8s. Lion Air has 10 in its fleet, and Garuda Indonesia has one, according to the DGCA notice. Both carriers have more on order.

Boeing 737 MAX 8s have already been under extra scrutiny by Indonesian authorities since just after the Lion Air accident. Investigators are focusing on faulty sensors, maintenance procedures, an automated flight-control augmentation system added to the MAX meant to help it perform similar to an NG, and the crew’s actions. There has been no indication so far that the two crashes are linked.

Cayman Airways president and CEO Fabian Whorms said the carrier “stands by our commitment to putting the safety of our passengers and crew first by maintaining complete and undoubtable safe operations, and as such, we have taken the decision to suspend operations of both our new Boeing 737 MAX 8 aircraft, effective from Monday March 11, 2019, until more information is received,” said the airline’s president and CEO Fabian Whorms.

Cayman has taken delivery of two MAX 8s—one in November and one last week. Its fleet also includes three 737-300s, Aviation Week’s Fleet Discovery shows.

Late on March 11, Brazil’s GOL said it would ground its seven MAX 8s, while Aeromexico announced it would pull its five 737 MAX 8s from service. The latest moves mean about 125 of the 371 MAX-family aircraft delivered have been grounded. 

While rare, isolated groundings by regulators or operators are not unprecedented. All Nippon Airways (ANA) and Japan Airlines (JAL) grounded their Boeing 787s just before FAA’s global 787 grounding in 2013. Qantas grounded its Airbus A380s in November 2010 following an inflight engine failure.

While FAA and major US and European airlines have not moved to park 737 MAXs, they face scrutiny. Association of Flight Attendants (AFA) President Sara Nelson, while cautioning that it is too early to draw “conclusions without all the facts” from the Ethiopian accident, is “formally requesting” the FAA to conduct “an investigation into the 737 MAX” in light of two accidents in five months involving the model.

“Crew and passengers are expressing concern about the 737 MAX 8 following a second crash, with similar characteristics to the Lion Air flight 610 crash," Nelson said in a March 11 statement. “While it is important that we not draw conclusions without all of the facts, in the wake of a second accident, regulators, manufacturers, and airlines must take steps to address concerns immediately. AFA is formally requesting the FAA conduct an investigation into the 737 MAX.”

AFA represents nearly 50,000 flight attendants and is part of the 700,000-member strong Communications Workers of America (CWA), AFL-CIO. Airlines represented include Chicago-based United Airlines and Seattle-based Alaska Airlines.

US-based MAX operators continue to express confidence in the model and Boeing.

“At this time there are no facts on the cause of the accident other than news reports,” American Airlines said March 11. “Our Flight, Flight Service, Tech Ops and Safety teams, along with the Allied Pilots Association and Association of Professional Flight Attendants will closely monitor the investigation in Ethiopia, which is our standard protocol for any aircraft accident. American continues to collaborate with the FAA and other regulatory authorities, as the safety of our team members and customers is our number one priority.”

Sean Broderick,