Read more live coverage on the crash and its aftermath here.

The A and B groups had already boarded Jesse Damiani’s Southwest Airlines flight, to New Orleans from Austin-Bergstrom International Airport, when President Trump announced that Boeing’s 737 Max plane was grounded.

“We were waiting for groups C and D to board when we got news,” he said in a phone interview.

The United States had been one of the few nations to allow the aircraft to fly after two planes of the same model were involved in deadly crashes in the past five months, including an Ethiopian Airlines crash on Sunday. Forty-two other nations had grounded the planes, as well as airlines around the world.

In a statement issued shortly after Mr. Trump’s announcement, the Federal Aviation Administration said that the decision was made using evidence found at the site of Sunday’s plane crash, as well as satellite data that was refined on Wednesday.

Domestically, travelers on specific routes offered by Southwest Airlines, American Airlines and United Airlines will be affected by this change. Air Canada and WestJet also fly Max 8 planes but had grounded them earlier on Wednesday.