American Airlines has agreed to buy up to 20 supersonic jets and put down a non-refundable deposit on the planes, which are still under construction and have been out of service for years.

Neither the airline nor the manufacturer, Boom Supersonic, provided financial details, including the amount of the US deposit.

Almost 20 years have passed since the last supersonic passenger flight of the Concorde, a British-French airliner that failed due to high costs – both for passengers and airlines.

Boom’s supersonic jets are designed to carry 65 to 80 passengers and fly more than 600 routes around the world in half the time.