DENVER (NewsNation Now) — The future of air travel could be changed forever with supersonic flight being reintroduced to regular air travel.

United Airlines aims to relaunch supersonic travel before the decade is over with a plane that has yet to be built and the promise travel time could be cut in half for cross-continental flights.

The airline said Thursday it would buy ultra-fast jets from Denver-based aerospace company Boom Supersonic, bringing back supersonic passenger travel which died out with the retirement of the Anglo-French Concorde in 2003.

Here’s what you should know:

What’s the big deal?

United Airlines said it will buy 15 “Overture” jets from Boom Supersonic once they meet United’s safety, operating and sustainability requirements, with an option for an additional 35 aircraft.

The Denver-based company said the planes will be capable of speeds up to 1.7 times the speed of sound, or about 1,300 mph. That is slower than the previously used supersonic plane but much faster than current airliners, which generally have cruising speed around or slightly above 500 mph.

The tentative plan is to rollout the Overture in 2025, have the first flight in 2026 and supersonic passenger travel by 2029.

How does supersonic travel compare to regular travel?

The Overture jets travel at twice the speed of today’s fastest passenger jets. United said flights between London and the New York area would be just three and a half hours instead of six and a half. A flight from San Francisco to Tokyo would be six hours instead of more than 10.

The passenger capacity would be from 65 to 88 people with a cruising altitude of 60,000 feet. Comparably, a Boeing 737 holds from 162 to 189 passengers.

While the plane hasn’t officially been built yet, the Overture plans to run on 100% sustainable aviation fuel. 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.

Boom’s Overture will be initially priced at business class fares, the company said.

In terms of comforts, Boom said the following: “the Overture onboard experience is designed for comfort, productivity and privacy, featuring in-seat entertainment screens, ample personal space, and contactless technology.”

Supersonic flight concerns

It has been nearly two decades since the last flight of the supersonic Concorde, which British Airways and Air France began using in 1976 to zip passengers in luxury across the Atlantic. The last one was retired in 2003, three years after an Air France Concorde crashed into a hotel shortly after takeoff from Paris, killing everyone on board and four people on the ground.

Supersonics have come under criticism from environmentalists for burning more fuel per passenger than comparable subsonic planes.

Several companies are working to come up with new supersonic jets that would be more economical on fuel — and create fewer climate-changing emissions — than the Concorde.

United, which has pledged to reduce its greenhouse gas emissions 100% by 2050, said the aircraft would be optimized to use 100% sustainable aviation fuel from its entry to service, projected to be in 2029.

The return of supersonic jets faces hurdles from regulators like the Federal Aviation Administration which must first give approval for them to fly at supersonic speeds over land, along with pressure from groups like airports that want the planes to be no noisier than comparable subsonic aircraft.

United’s head of corporate development, Mike Leskinen, told The Air Current in an interview that the transaction was not a firm order but it involved United taking the lead on “a real aircraft” project.

A Boom spokeswoman said the order meets the terms of a commercial agreement.

United said the move reflected a strategy to invest in sustainable air travel.