In an abrupt shift, Boeing said Tuesday it is recommending that all 737 Max pilots undergo simulator training before they resume flying the jets — a decision that could further delay the plane’s return to service.

In making the announcement, the company’s interim chief executive officer, Greg Smith, said he believed requiring simulator training would build confidence in the jetliner, which was grounded in March after two fatal crashes that killed 346 people.

“Safety is Boeing’s top priority,” Smith said in an emailed statement. “Public, customer and stakeholder confidence in the 737 MAX is critically important to us and with that focus Boeing has decided to recommend MAX simulator training combined with computer-based training for all pilots prior to returning the MAX safely to service.”

The announcement is a reversal for the company, which had long maintained that mandatory simulator training was not necessary for the jet’s safe return to service.

In fact, one of the original selling points of the Max, the newest version of Boeing’s popular 737 jet, was that it was so similar to previous versions of the plane that pilots only needed to take a one-hour course on an iPad to fly it.

Boeing’s announcement came amid reports in the Wall Street Journal that federal regulators were increasingly leaning toward requiring simulator training. That, too, was a shift. As recently as August, it appeared that the Federal Aviation Administration would require only computer-based training for pilots, even as some international regulators said they wanted their pilots to undergo simulator training.

The FAA, which will have the final say in the matter, said Tuesday that no decision on pilot training has been made and that it will consider Boeing’s recommendation.

“The agency will consider Boeing’s recommendations for flight crew simulator training during the upcoming Joint Operations Evaluation Board (JOEB), a key component of the ongoing certification work that includes U.S. and foreign air carrier flight crews,” said Lynn Lunsford, an FAA spokesman. “Data from those tests will be used to develop a Flight Standardization Board (FSB) report that will detail the FAA’s official recommendations for training.”

The 737 Max was grounded worldwide nearly 10 months ago after the crash of an Ethiopian Airlines flight on March 10. It was the second fatal crash of a 737 Max in less than five months. In October 2018, a Lion Air flight crashed off the coast of Indonesia, killing all aboard.

Rep. Peter A. DeFazio, (D-Ore.), the chairman of the House Transportation and Infrastructure Committee, welcomed Boeing’s announcement but expressed frustration that it has taken the company so long to determine that simulator training is needed.

“While I agree with Boeing’s decision to recommend that pilots undergo simulator training on the MAX, it’s remarkable that it took two deadly crashes, numerous investigations and untold public pressure before Boeing arrived at this decision,” he said in a statement. “Boeing’s business model for the 737 MAX was premised on Boeing’s unreasonable, cost-saving assurance to airlines that pilots qualified to fly a different 737 variant, the 737 Next Generation, should not undergo simulator training to fly the 737 MAX. Boeing made a fundamentally flawed decision that put production and profits ahead of the public’s safety.”

In the months since the two deadly crashes, the Chicago-based company has struggled to contain fallout from the crisis. In December, it abruptly fired chief executive Dennis Muilenburg and replaced him with David L. Calhoun, who is CEO-designate. He had served as the company’s chairman. Calhoun is expected to assume the top job at the company next week. Several other top Boeing executives, including its chief engineer and the vice president in charge of the 737 Max program, have left the company.

In addition to approving new pilot training requirements, the FAA has the responsibility of approving or rejecting software changes Boeing is making to the Maneuvering Characteristics Augmentation System (MCAS), a flight control system that has been implicated in both crashes. Investigators think that in each crash, MCAS repeatedly pitched the plane’s nose downward after receiving erroneous information from one of the jet’s angle-of-attack sensors, making it impossible for pilots to regain control of the aircraft.

Requiring simulator training could complicate the plane’s return to service and could be costly, experts said.

“Any kind of flight training is an expensive proposition,” said Michael Wiggins, the chairman of the Department of Aeronautical Science at Embry-Riddle Aeronautical University. “Simulators are one way to save money because [pilots] don’t have to take a plane and can train in scenarios that pilots don’t want to have to do in a real plane.”

Even so, Kit Darby, an Atlanta-based aviation consultant, estimated that requiring simulator training for the estimated 16,000 pilots at the three U.S. airlines that use the 737 Max could cost $35 million. But, he added, the costs could vary depending on the circumstances. The simulators can range in cost from $10 million to $14 million and can take a year to build, he added.

Another challenge is whether airlines have enough available Max simulators.

A spokeswoman for Southwest Airlines said the carrier has three simulators in various stages of FAA certification and expects to receive another three simulators later this year. Southwest has the most 737 Max jets — 34 — in its fleet of any U.S. carrier.

United Airlines has one operational Max simulator and three on order, but the company said it will be able to cover its pilot training needs with other 737 simulators it has on hand.

Airline officials said it was too early to determine how the mandatory simulator training would affect the 737 Max jet’s return to service.

“Teams within Southwest have been modeling scenarios for both simulator and computer-based training programs to ensure we’re ready to comply with final recommendations and guidance from the federal regulators,” said Brandy King, a spokeswoman for Southwest Airlines. “Cost and timing estimates are premature to share ahead of that specific guidance.”

Last month, Southwest and American Airlines removed the Max jets from their schedules through April, while United removed the plane from its schedule through June.

Families of the crash victims expressed relief that Boeing has changed its position on simulator training but said more needs to be done.

“The Flight ET302 victims’ families have requested simulator training for pilots for many months,” said Michael Stumo, whose daughter, Samya Stumo, 24, died in the Ethio­pian Airlines crash. “We are glad Boeing is no longer opposing this training.”