Boeing Co.’s 737 Max is poised to return to service at United Airlines Holdings Inc., the second U.S. carrier to restart flights after a record-long grounding prompted by two deadly crashes.

United is planning a total of two dozen flights on the Max from its hubs in Denver and Houston on Thursday, less than two months since American Airlines Group Inc. began operating the plane again on a single route between Miami and New York. Next month, Southwest Airlines Co. is expected to resume Max operations and Alaska Air Group Inc. will start its first service with the model.

The flights further the gradual and so far uneventful return of Boeing’s best-selling plane after a 20-month flying ban, the longest jetliner grounding in U.S. history. The Max accounts for about 80 per cent of Boeing’s backlog of orders and represents the company’s only offering in the crucial single-aisle market, in which the U.S. planemaker trails Airbus SE. The model was grounded in March 2019 after two crashes killed 346 people.

United is scheduled to operate 566 Max flights this month and the tally will increase to nearly 2,000 in March, according to data compiled by Cirium, an aviation analytics company.

Worldwide, seven airlines have scheduled 3,996 Max flights this month, up from four carriers that made about 2,450 flights in January, according to Cirium. Almost 8,700 Max trips are scheduled next month.

Customer Options

United, which has 21 Max jets in its fleet and plans to take another two dozen this year, hasn’t seen a notable trend of customers booking away from the aircraft, a spokesman said. The Chicago-based airline is offering customers two options to select alternate flights if they’re not comfortable flying the Max -- once during booking and again when they’re notified about their trip a week before the flight.

Brazil’s Gol Linhas Aereas Inteligentes SA was the first to start flying the Max again last year, and Grupo Aeromexico SAB also resumed operations shortly before American.

In Canada, WestJet Airlines returned the plane to service Jan. 21, with flights between Calgary and Toronto. Air Canada followed Feb. 1 with service on five domestic routes from Toronto.

The European Union’s aviation-safety regulator cleared the Max for service last month. On Feb. 25, Czech airline Smartwings AS plans service between Prague and Mallorca on its Max 8 planes.

Regulators in China, the first nation to ground the jet, have yet to offer a timetable for when they may certify the jet to resume commercial service. Across Asia, no airlines have scheduled Max flights this year, according to Cirium.