American Airlines has agreed to buy up to 20 supersonic jets and put down a non-refundable deposit on the planes that are still on the drawing board and years away from flying.

Neither American nor the manufacturer Boom Supersonic would provide financial details on  Tuesday, including the size of American’s deposit. American becomes the second US customer for Boom after a similar announcement last year from United Airlines for 15 of the planes, called the Overture.

It has been nearly 20 years since the last supersonic passenger flight by Concorde, the British-French plane that failed to catch on because of the high cost of flights.

Boom CEO Blake Scholl insists his company’s plane will be different when it debuts in 2029, with tickets costing about $4,000 to $5,000 to fly from New York to London in about three and one-half hours.

“There are tens of millions of passengers every year flying in business class on routes where Overture will give a big speed-up,” Scholl said in an interview, “and airlines will be able to do it profitably.”

Skeptics have questioned Boom’s ambitious timetable, especially in light of the many years it has taken Boeing, an established manufacturer, to get planes or even retrofits to planes approved by the Federal Aviation Administration. Boom says the Overture program will cost between $6 billion and $8 billion. The plane carries a list price of $200 million, although other manufacturers routinely give airlines deep discounts.

Last month, Boom announced changes to the plane’s design to make it simpler and less expensive to build and maintain. The most striking change was going from three engines, including a different type on the tail, to four identical engines under the delta-shaped wings.

However, Boom does not yet have an engine manufacturer lined up. It is talking with Rolls Royce and others.

Meanwhile, the Federal Aviation Administration said Monday that it was reducing flights in the area around New York City because of lack of staffing.

Departing and arriving flights could be delayed up to two hours at John F. Kennedy International, LaGuardia and Newark (New Jersey) Liberty International airports, the FAA said.

The agency said passengers should check with their airline for information about particular flights. “Due to the availability of staff tonight, the FAA must reduce the flow of aircraft in certain airspace serving New York City to maintain safety,” the FAA said in a statement Monday afternoon.

The statement implied that the shortage was expected in air-traffic controllers, but the FAA did not specify which employees were out, and a spokeswoman did not immediately reply when asked for more details.

Flights at LaGuardia were being stopped for more than an hour, and planes at Newark were facing average delays of 44 minutes by late afternoon, according to an FAA website. Airlines and the FAA have traded blame for flight delays and cancellations this summer. Much of the airlines’ charges have focused on a flight-control center in Jacksonville, Florida. The FAA has promised to increase staffing there.

Spirit Airlines and Frontier Airlines have said that FAA staffing issues have prevented them from operating all the flights to Florida that they would like to schedule.

Until the FAA announcement, Monday had been a better-than-usual day for the nation’s air-travel system. About 200 flights nationwide had been canceled and nearly 3,500 other flights had been delayed, according to the FlightAware tracking service. The average day in August, through Sunday, included about 670 cancellations and more than 6,200 delays.

Meanwhile, a recovery in global business travel spending to pre-pandemic levels is likely to be delayed by 18 months to 2026 because of factors like persistent inflation, high energy prices, labour shortages and lockdowns in China, a new industry forecast shows.

The Global Business Travel Association (GBTA) said business travel spending rebounded by 5.5% to $697 billion in 2021 with North America leading the recovery, but remained well short of 2019 levels of $1.4 trillion.

The recovery outlook is more pessimistic than GBTA’s last forecast issued a year ago, when it expected a full rebound to 2019 levels by 2024.

Environmental sustainability considerations and the regional impact of the war in Ukraine are also weighing on travel demand, the forecast said.

“The factors impacting many industries around the world are also anticipated to impact global business travel recovery into 2025,” GBTA CEO Suzanne Neufang said in a statement. “The forecasted result is we’ll get close, but we won’t reach and exceed 2019’s pre-pandemic levels until 2026.”