An image of a supersonic airplane (Photo courtesy of Boom)

Business and first-class travelers could soon fly between London and New York aboard a supersonic commercial airplane in about 2.5 hours, according to one start-up — that’s less time than it takes to watch a “Lord of the Rings” movie.

Boom, an aerospace company based in Denver, said at the Paris Air Show on Tuesday that passengers could make the ultra-fast trip across the pond within the next six years, if it’s able to pass all certification hurdles.

The company also aims to shuttle passengers from San Francisco to Tokyo, gate-to-gate, in 5.5 hours, vs. the current 11-hour travel time. Flights from Los Angeles to Sydney would take just under seven hours, compared with the current 15.

“Airlines are excited for something new and different to offer their passengers — and we’re thrilled that major world airlines share our vision for a future of faster, more accessible supersonic travel,” Blake Scholl, Boom’s founder and chief executive, said at the show.

Five airlines have already placed more than 70 orders for Boom’s faster-than-sound passenger airliners, the company announced at the air show. The 76 aircraft reservations were made by Virgin, which booked 10 planes, and four other airlines that will be announced in the coming months, the company said.

Some experts, however, are skeptical that Boom can deliver on its vision and offer a product that makes financial sense. The European aircraft Concorde, which ended its transatlantic supersonic flight in 2003, was never commercially viable, and with airfare at $20,000, appealed to only a very narrow slice of travelers, said Robert W. Mann Jr., an independent airline industry analyst and consultant. Fuel economy, unproven technology, challenging routing times, and regulations against supersonic commercial flight are key obstacles Boom faces, Mann said.

“These are not commercially off-the-shelf programs or capabilities,” said Mann.

There are also some travel limitations. The United States and many other countries do not allow supersonic commercial flights over land, because of the loud shock wave that can pose a nuisance to communities below. But a Boom spokesman said that its passenger airliner is being designed to minimize the noise it makes and that Boom will work to change those regulations.

The company said that it will succeed where Concorde failed because Boom is using better engines and improved aerodynamics and materials to help reduce the costs of operating and maintaining its aircraft. And a business-class ticket from New York to London could cost $5,000, Boom estimates, far less than the $20,000 charged by Concorde.

And as for coach-airfare seats, they wouldn’t be economically feasible for Boom to offer with the first wave of these planes, the spokesman said, but the company could in the future.