United Airlines (UA, Chicago O'Hare) is buying ultra-fast jets from Denver-based aerospace company Boom Technology (Denver Centennial) in a move that will bring back supersonic travel - something last seen when the well-heeled jetted across the Atlantic in the Concorde almost 20 years ago.

Under the terms of the agreement announced on June 3, United will purchase 15 of Boom's “Overture'” airliners once they meet United's safety, operating, and sustainability requirements, with an option for an additional 35 aircraft. The companies will work together on meeting those requirements before delivery.

The terms of the deal were not disclosed. Still, United's head of corporate development, Mike Leskinen, told The Air Current that while deposits have been paid, financial protection for United has been built into the agreement.

Once operational, Overture is expected to be the first large commercial aircraft to be net-zero carbon from day one, optimised to run on 100% sustainable aviation fuel (SAF) at twice the speed of today's fastest passenger jets.

It is slated to roll out in 2025, fly in 2026, and is expected to carry passengers by 2029. The ultimate hurdle will be winning certification by regulators, including the Federal Aviation Administration (FAA).

United and Boom are to work together to accelerate the production of greater supplies of SAF. Currently, commercial aircraft engines are certified to fly with 50% of alternative fuel, with the rest using ordinary kerosene, but available supplies fall far short of that level, Reuters reports.

The deal is punted as the world's first purchase agreement for net-zero carbon supersonic aircraft. "United continues on its trajectory to build a more innovative, sustainable airline, and today's advancements in technology are making it more viable for that to include supersonic planes. Boom's vision for the future of commercial aviation, combined with the industry's most robust route network in the world, will give business and leisure travellers access to a stellar flight experience," said United Chief Executive Officer Scott Kirby.

Capable of flying at speeds of Mach 1.7, Overture will be able to connect more than 500 destinations in nearly half the time. Amongst the many future potential routes for United would be New York Newark to London Heathrow in just three and a half hours, Newark to Frankfurt International in four hours, and San Francisco to Tokyo Narita in just six hours.

Overture's order book, including purchases and options, stands at 70 aircraft, and Boom is working with the United States Air Force (MC, Washington National) for government applications of Overture.

XB-1, a demonstrator aircraft, rolled out in 2020, and its net-zero carbon flight test programme is underway. The company is backed by investors such as Bessemer Venture Partners, Prime Movers Lab, Emerson Collective, and American Express Ventures.

However, neither company made any mention about the expected operating cost of the new supersonic aircraft, one of the major issues that negatively affected the success of the Anglo-French Concorde, which flew commercial flights from 1976 until October 2003. The cost of fuel eventually exceeded the profit made from the flights and rendered Concorde unprofitable to operate.