Flexjet has placed a firm order valued at $2.4 billion for 20 Aerion AS2 supersonic jets, with delivery to begin in 2023. First flight is expected in 2021.

Flexjet CEO Kenn Ricci said the company will use the supersonic jet for overseas flights and also in China, which does not have restrictions on sonic booms.

Customers are already excited about the jet, he said. They immediately began citing city pairs where they would like to fly. But no one wants to fly it subsonically, Ricci said. The AS2 can fly subsonically over land in the U.S., Europe and areas where the boom is restricted. But it won’t be cost-effective to do so.

The three-engine jet will burn a high amount of fuel, roughly 1,000 gal. per hr., and its long length will restrict its use at some airports, Ricci said. “It’s still going to be an expensive plane to operate,” he said. Still, with the aircraft traveling at Mach 1.2, its boom will not touch the ground, Ricci said. Because of that, regulators may be able to be convinced to allow the jet to fly supersonically across the country, he said. Even so, the aircraft can be placed at points on the Atlantic and Pacific for international travel.

Flexjet placed a down payment with the order. As the program progresses and milestones are met, it will put more money down.

The aircraft will carry eight to 12 passengers and have a top speed of Mach 1.5, which is 67% faster than the top cruise speeds of current or anticipated long-range subsonic jets, Aerion said. It will have a range of 4,750 nm at supersonic speeds, which will save three hours flying across the Atlantic versus subsonic aircraft and more than six hours on longer transpacific flights.

The jet is under development by Aerion in collaboration with Airbus Group.