“The safety of the American people and all people is our paramount concern,” Trump said Wednesday at the White House. “Hopefully they will very quickly come up with the answer but until they do the planes are grounded.”

The move is a major blow to Boeing, which has lost billions of dollars in value this week as nation after nation announced they were barring the aircraft from flying. The Federal Aviation Administration’s expected action followed Canada’s decision to halt Max flights earlier Wednesday.

Canada Transport Minister Marc Garneau said Wednesday in Ottawa that satellites that tracked the Ethiopian Airlines flight suggest possible “similarities” with a Lion Air crash on Oct 29. A Lion Air Max 8 crashed off the coast of Indonesia, killing all 189 people aboard, following a malfunction of a software feature on the plane that repeatedly forced it into a dive.

Boeing touched a session low on the news, falling as much as 2.8 percent.

The FAA and other aviation regulators around the world took several steps after that crash to notify pilots of the Maneuvering Characteristics Augmentation System, or MCAS, and to remind them how to overcome it in the event of a malfunction. However, a more formal fix to redesign it won’t be mandated until April, the FAA said Monday.

All 157 people aboard the Ethiopian Airlines 737 Max 8 died when it plunged into the ground at high speed about six minutes after takeoff near Addis Ababa. Investigators have released no information about what caused the crash.

The single-aisle Max family is the Chicago-based planemaker’s largest seller and accounts for almost one-third of the company’s operating profit.

The last fleet-wide grounding by the FAA occurred on Jan. 17, 2013, when it ordered a halt to revenue flights by Boeing’s then-new model, the mostly composite 787, after a lithium-ion batteries on the plane overheated. Prior to that, the last such action halting flights on a fleet occurred in 1979 on the Douglas DC-10. DM