NASA Administrator Jim Bridenstine testifiies before the Senate Commerce, Science and Transportation Committee on Wednesday. (Chip Somodevilla/Getty Images)

NASA Administrator Jim Bridenstine on Wednesday brushed aside concerns about the safety of the Boeing 737 Max 8, telling a Senate committee that consumers are free to change their flights if they are worried about flying aboard the aircraft.

Bridenstine was speaking hours before President Trump announced that all of the aircraft would be grounded until further notice. “The safety of the American people, and all people, is our paramount concern,” Trump said in announcing the order, which will ground more than 70 aircraft.

Later Wednesday, two key lawmakers who were earlier skeptical of other countries’ decisions to ground the planes praised Trump’s move and called for a “rigorous investigation.”

At a hearing of the Senate Commerce, Science and Transportation Committee, Bridenstine said he would have no qualms about flying in one of the planes, even as aviation officials in Europe and around the world had ordered hundreds of Boeing aircraft grounded.

Investigators are working to find the cause of this week’s Ethio­pian Airlines crash of a 737 Max 8 that killed 157 people.

“I’m going to be flying in the coming days,” Bridenstine said in response to questions from Sen. Richard Blumenthal (D-Conn.) at the hearing, which was focused on space exploration commerce. “And when I fly, if I’m on a 737 Max 8, I think I’d be perfectly okay and it wouldn’t bother me.”

Asked whether other passengers should be allowed to choose another flight to avoid that aircraft, Bridenstine replied, “Absolutely.” But he declined to say whether he believed they should be able to do so free of charge.

“Oh, I don't know about that. Certainly, it’s a free market out there, and if people want to ride on a different airplane, they should,” he said.

The United States and its carriers had been the last major users of the aircraft. Canada’s transportation minister grounded all Boeing 737 Max 8 planes earlier Wednesday.

The plane, Boeing’s newest, has been involved in two crashes in less than six months. In October 189 people were killed when a 737 Max 8 crashed off the coast of Indonesia during Lion Air flight.

Transportation Secretary Elaine Chao was spotted flying from Austin, to Washington on Tuesday aboard one of the aircraft, Politico reported.

Ahead of Trump’s announcement, a handful of lawmakers of both parties had called for the aircraft to be banned from U.S. airspace. Others, such as Sen. Richard C. Shelby (R-Ala.), had voiced concern about the planes while stopping short of calling for them to be grounded.

“I don’t want to fly in one right now. ... I think they got a safety problem, and they need to fix it,” Shelby told reporters Wednesday afternoon.

Sen. Roger Wicker (R-Miss.) announced Tuesday that the Commerce, Science, and Transportation Committee would hold a hearing in the coming days “reviewing the state of aviation safety to ensure that safety is maintained for all travelers.” He told reporters that he had not yet decided who the witnesses will be.

Trump’s announcement received bipartisan praise on Wednesday — including from lawmakers who had previously voiced skepticism of other countries’ decision to ground the planes.

Rep. Rick Larsen (D-Wash.), the chairman of the House Transportation and Infrastructure Committee, and Rep. Peter DeFazio (D-Ore.), the chairman of the panel’s Subcommittee on Aviation, said in a joint statement that “despite repeated assurances from the FAA,” it was “abundantly clear” that the aircraft should be grounded.

“We plan to conduct rigorous oversight with every tool at our disposal to get to the bottom of the FAA’s decision-making process,” the lawmakers said, calling for “a rigorous investigation into why the aircraft, which has critical safety systems that did not exist on prior models, was certified without requiring additional pilot training.”

DeFazio said earlier Wednesday that acting FAA Administrator Daniel K. Elwell had claimed “firmly” in conversations with him that there had not been an incident involving systemic issues with the Boeing 737 Max 8 in the United States “with over 40,000 hours of flight.”

Larsen had previously been critical of other countries’ decision to ground the planes, saying, “It’s very difficult to separate emotion from expertise on this issue.”

“The other countries grounding the 737, it’s their decision,” he said. “It doesn’t seem to be a decision based on anything happening in their countries with the experience of their flying public or of their pilots. But I do understand why they would ground them. But in terms of what’s going on in the U.S., until the FAA says something different ... I would get on that airplane.”

Blumenthal, who had been vocal in calling for the flights to be grounded, said in a statement that Trump’s move was “unacceptably overdue” and called for consumers to be given “prompt refunds for canceled flights and options to change flights at no cost.”

Erica Werner, Michael Laris and Luz Lazo contributed to this report.