American Airlines places deposits on 20 Boom Supersonic planes

American Airlines is putting down a non-refundable deposit on 20 supersonic jets that are still on the drawing board with manufacturer Boom Supersonic.

There were no financial details provided by either firm.

American, which also took options for 40 more Boom Overture planes, becomes the second US customer for Boom after United Airlines, which is buying 15 jets.

The last supersonic passenger flight by Concorde, the British-French plane that failed to catch on due to high costs for both passengers and airlines, was nearly 20 years ago.

Boom CEO Blake Scholl insists that his company's plane will be unique when it debuts in 2029, with tickets costing between $4,000 and $5,000 to fly from New York to London in three and a half hours.

Boom claims its plane will reach 1.7 times the speed of sound, or about 1,300 mph, and carry 65 to 80 passengers.

Skeptics have questioned Boom's timeline, particularly given how long it has taken Boeing to get planes or even retrofits approved by the Federal Aviation Administration.

The Denver-based Boom, which does not yet have an engine manufacturer lined up, is talking with Rolls Royce and others.

Richard Aboulafia, an aerospace analyst at consultant AeroDynamic Advisory, insists that with a supersonic jet, an engine design should come ahead of designing a plane.

According to Boom, the plane will run entirely on sustainable aviation fuel, which is often made from the plant material and is currently in short supply and very expensive.

According to Boom, the program will cost between $6 billion and $8 billion. The plane has a list price of $200 million, but other manufacturers routinely offer significant discounts to airlines.

Boom announced changes to the plane's design last month to make it easier and less expensive to build and maintain. The most noticeable change was the transition from three engines, one of which was unique to the tail, to four identical engines beneath the delta-shaped wings.