Delta Air Lines orders 100 Boeing 737 Max planes.

Delta Air Lines said on Monday that it planned to buy 100 of the largest variant of Boeing’s 737 Max, even as Boeing races to secure regulatory approval for that version of the jet by the end of the year.

The order is Delta’s first for the Max and a boon for Boeing. A nearly two-year global ban on the plane, prompted by two fatal crashes, contributed to Boeing slipping behind in a competition for orders against its rival Airbus. In late 2020, the Federal Aviation Administration allowed two midsize versions of the plane — the Max 8 and Max 9 — to fly again once certain fixes were made.

Delta’s order is for the Max 10, the biggest variant of the plane. If Boeing is unable to secure regulatory approval for the plane by a December deadline, it would have to make significant changes to flight deck alert systems under a recently passed law, unless Congress intervenes. That would eliminate a key selling point of the plane: Its similarity with other Max variants, which would eliminate the need for pilots to be trained separately for each model of the plane.

Delta expects to receive the first deliveries of the plane in 2025. At list prices, the order is valued at nearly $13.5 billion, though Boeing typically discounts such large orders.

In an interview this month with Aviation Week, Boeing’s chief executive, Dave Calhoun, said he was optimistic that Boeing would be able to proceed without a flight deck overhaul, but signaled an openness to canceling the Max 10 if not. Delta said in a statement it had “adequate protection in place” in case of any delay in the expected certification of the Max 10, including shifting to a different Max model.

Delta said the order, which includes an option for an additional 30 planes, served its long-term strategy. The Max 10 is expected to deliver “economic benefits” because of its ability to carry more passengers on a given trip and will be 20 percent to 30 percent more fuel efficient than the planes it will replace, the airline said. Nearly a third of the seats on the Max 10 will be in first class or Delta Comfort+, serving the airline’s focus on premium travel.

“The Boeing 737-10 will be an important addition to Delta’s fleet as we shape a more sustainable future for air travel, with an elevated customer experience, improved fuel efficiency and best-in-class performance,” Ed Bastian, Delta’s chief executive, said.