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Frustrated passengers were taken off planes, and in some cases stranded at airports, after the Federal Aviation Administration issued an emergency order grounding Boeing 737 Max jets in the wake of an Ethiopian Airlines crash Sunday and a previous deadly accident in Indonesia.

President Donald Trump announced the order on Wednesday, and U.S. airlines acknowledged that it would lead to canceled flights around the country.

One woman, Amber H., 22, who didn't feel comfortable giving her full last name, told NBC News that her Southwest Airlines flight to Orlando, Florida, was headed to the runway at Reagan National Airport in Washington when the order came down.

"The pilot already had explained that we were on one of the Boeing 737 Max 8 planes but that he was confident in his ability to fly it," she said. "Not even 10 minutes later, he announced that we had to go back" because of the emergency order.

Amber said she expected to miss a few days of work because she wasn't able to book a direct flight to Orlando until Saturday.

The FAA said it decided to ground the jets after it found that the Ethiopian Airlines aircraft that crashed Sunday, killing 157 people, had a flight pattern very similar to that of the plane in the Lion Air accident in Indonesia in October, which killed 189 people.

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Another passenger in Washington, Ethan Levin, told NBC Washington that he found out about the FAA order from his father.

"My dad called me, and he told me that all of the 737s were being grounded by Trump, so we didn't get an announcement till, like, 10 minutes later after that call," Levin said.

Southwest Airlines has the most flights with the Boeing Max series aircraft in the United States, about 150 flights per day, out of the airline's total of about 4,100 flights daily. American Airlines has roughly 85 flights a day on the Boeing Max 8 and Max 9 jets. United Airlines has about 40 such flights.

Max 8s and Max 9s make up about 8 percent of all of Southwest's arrivals and departures at St. Louis Lambert International Airport, where Saran Donahoo said she didn't find out she was aboard one of the affected flights until she'd already boarded.

"While we were waiting, I was reading the little brochure they have on the back of the seat, and I was like, 'uh huh,'" Donahoo told NBC affiliate KSDK. "Then my brain said, 'Wait — it's the same plane.'"

By then, it was too late to make a change, so "I just prayed we'd be OK and let it go," Donahoo said.

Fadia Shashan, a passenger on a 737 Max 8 that flew from Las Vegas to Houston, said passengers weren't told about the emergency order until after they landed at William P. Hobby Airport.

"It's terrifying, you know," Shashan told NBC affiliate KPRC of Houston.

Another passenger, Lars Gunnar, flew on a 737 Max 8 to Nashville International Airport in Tennessee on Wednesday.

"I had faith in the flight checks and just kind of hoped for the best," Gunnar told NBC affiliate WSMV of Nashville. He said that as he was in the air, he could only hope that "it was quick if anything happened."

Tim Pettitt didn't even know he had been on an affected flight until his family filled him in upon his arrival Wednesday at Tampa International Airport in Florida.

"My wife and my son told me," Pettitt told NBC affiliate WFLA. "They said, 'Dad, you were on one of those planes,' so I'm glad I made it."

The FAA order followed similar directives from a growing number of countries around the world — including Canada, European nations and China — after Sunday's crash.

Boeing Co. said it supported the order and had recommended that the FAA ground its entire global fleet of 371 Max 8 and Max 9 jets.

"Boeing has determined — out of an abundance of caution and in order to reassure the flying public of the aircraft's safety — to recommend to the FAA the temporary suspension of operations of the entire global fleet," it said.