Boeing Co.  (BA) 737 Max 8 and Max 9 planes will be grounded by the U.S. government for an indefinite time, President Donald Trump told reporters Wednesday.

The order follows the crash this past weekend in Africa of an Ethiopian Airlines 737 Max 8 that killed 157 people and was the second crash of a Max 8 in five months.

“We’re going to be issuing an emergency order of prohibition to ground all flights of the 737 Max 8 and the 737 Max 9,” Trump told reporters in Washington on Wednesday.

"The safety of the American people and all people is our paramount concern," Trump said, adding shortly after, that "Boeing is an incredible company. They are working very, very hard right now."'

Trump said the order was effective immediately, but that any of those planes currently in the air would continue to their destination, and then would be grounded.

Shares of Boeing were down 2.34 percent to $367.06 shortly after the president spoke.

Why It's Important

Several European countries, including France and Germany, as well as Canada, Britain and China had already moved to ground flights of the aircraft, but the U.S. Federal Aviation Administration had said earlier Wednesday it was yet to see a need to do the same. Several smaller countries had also closed their airspace to the planes.

The two U.S. airlines that fly the 737 Max, American Airlines Group Inc AAL and Southwest Airlines Co. LUV both sold off after the announcement.

Boeing released a statement saying it agreed with the order - that it had determined "out of an abundance of caution and in order to reassure the flying public of the aircraft’s safety" to recommend the plane be grounded, after earlier saying it didn't see any reason to take the plane out of service.

There are 371 737 Max 8 and 9 jets flying around the world.

The New York Times reported Wednesday the pilot of the Ethiopian airliner had reported flight control problems shortly after taking off from Addis Ababa’s Bole International Airport on Sunday. The plane crashed a few minutes later killing everyone aboard.

Officials quickly said it was similar to the crash of another 737 Max 8 in October in which 189 people were killed when Lion Air Flight 610 went down in the Java Sea.