Supersonic transatlantic flights are set to return by the end of the decade, according to a US airline.
United Airlines announced it has conditionally agreed to buy planes capable of flying at speeds of Mach 1.7, which is twice as fast as modern airliners.
The firm said potential routes include Newark, New Jersey to London in just three-and-a-half hours.
Flights between those locations currently take nearly seven hours.
The fastest flight by a commercial airline between New York – which neighbours Newark – and London is two hours, 52 minutes and 59 seconds, set by Concorde in 1996.
But Concorde was retired from service in October 2003, with British Airways and Air France blaming a downturn in passenger numbers and rising maintenance costs.
United has agreed to purchase 15 Overture airliners made by US firm Boom Supersonic, once they meet “demanding safety, operating and sustainability requirements”.
It has an option for an additional 35 planes.
Overture is expected to be the first large commercial aircraft to have zero carbon emissions by running on pure sustainable aviation fuel, United said.
Flight trials are scheduled to begin in 2026, with commercial use beginning three years later.
United chief executive Scott Kirby said: “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.
“Our mission has always been about connecting people and now, working with Boom, we’ll be able to do that on an even greater scale.”
Boom Supersonic founder and chief executive Blake Scholl said: “The world’s first purchase agreement for net-zero carbon supersonic aircraft marks a significant step toward our mission to create a more accessible world.
“United and Boom share a common purpose – to unite the world safely and sustainably.
“At speeds twice as fast, United passengers will experience all the advantages of life lived in person, from deeper, more productive business relationships to longer, more relaxing vacations to far-off destinations.”