American Airlines will buy up to 20 jets from Boom Supersonic, an aircraft maker that aims to commercialize supersonic, and super-fast, flight.

Boom's Overture four-engine jets promise speeds of up to Mach 1.7 over water, which is twice the speed of today's fastest commercial aircraft -- meaning the jet can fly from Miami to London in just under five hours, rather than the standard nine hours.

About a year ago, United Airlines also agreed to purchase some 15 Boom jets, and in 2016, Virgin Atlantic partnered with Boom to build and test planes in an attempt to make the historically expensive flights more affordable.

With the American Airlines deal in hand, Boom has an order of 130 planes to fill, including options -- American has an option to purchase 40 more of the jets -- valued at about $26 billion, Reuters reports. Boom's Overture jets, which can carry 65 to 80 passengers, are expected to start coming off Boom's Greensboro, North Carolina, production line in 2025, followed by test flights in 2026. Boom expects its jets to carry their first passengers in 2029, but Boom has already been delayed in conducting test flights for its other jet, the XB-1, so delivery for the Overture might also be delayed.

Boom's jets, while incredibly fast, are not as fast as the legendary Concorde's, which flew at a speed of Mach 2.04. The Concorde, which made its first supersonic flight in 1976 from New York City to London in three hours, was in the skies until 2003, when the Concorde made its last commercial flight, due to a number of issues with the jets. For one, the flights were expensive to operate and used too much fuel, meaning they would cost thousands of dollars for a ticket. Concorde jets were also incredibly loud due to their "sonic booms" -- so loud, in fact, that the Federal Aviation Administration (FAA) banned overland supersonic commercial flights.

Boom's Overture will fly over land at a rate that's about 20% faster than subsonic flights, but not as fast as it will on the over 600 mostly transoceanic routes to which Overture will be best suited.