Blake Scholl, CEO of jet startup Boom Supersonic, wants to create a golden age of air travel—one that’s more environmentally friendly and, most importantly, faster. Passengers would be able to get from New York to London in just three-and-a-half hours—half the usual time—and from San Francisco to Tokyo in a mere six hours.

His company, which is on a quest to build a passenger jet that can travel at Mach 1.7, achieved a major milestone earlier this month by cutting a historic deal with United Airlines. The airline agreed to spend $3 billion on 15 planes that can carry up to 88 passengers for nearly 5,000 miles.

“United is the first commercial airline to place a firm order for civilian supersonic aircraft since the 1970s,” Scholl said.

But can a six-year-old startup with only 150 employees and a relatively paltry—by aerospace standards—$270 million in funding build a supersonic jet from scratch? Commercial airliners, with their millions of parts, are notoriously difficult to produce. Creating one that can travel at supersonic speeds only adds to the complications. Then there are a host of regulatory and safety hurdles that must be cleared.

Perhaps unsurprisingly, Boom Supersonic is already years behind schedule because of technical problems. Flight testing of a scaled-down version of its jet, which was originally planned for 2017, has been pushed back to later this year or early next year.

“It costs billions of dollars to build an aircraft like this and requires funding from government and the public markets,” said Rob Meyerson, a former president of Amazon founder Jeff Bezos’s space startup Blue Origin and an adviser to Hermeus, a startup trying to build private jets that can fly from New York to London in 90 minutes.

“Funding for supersonics has been waning since the 1990s, but in the last three years, in a push to lead other countries, there's been significant government investment in hypersonics—aircraft that can fly faster than Mach 5.”

The last supersonic airliner was the Concorde, built by Aérospatiale (now part of Airbus) and British Aircraft Corporation with backing by the French and British governments. It flew luxury transatlantic flights starting in 1976, primarily from New York and D.C. to London and Paris, at more than twice the speed of sound. The planes—only 14 were ever produced—were ultimately grounded in 2003, a few years after a devastating crash in 2000 killed all onboard, and after the planes were deemed too expensive and too noisy to operate.

Scholl says Boom Supersonic will avoid many of Concorde’s pitfalls. He said that his company’s planes, called Overture, will cost only $200 million each to buy, or the same as a Boeing 767. His goal is to make high-speed travel more accessible, based on a hope that airlines will charge business-class fares or less. By contrast, fares on the Concorde were more than double in today’s dollars, making the caviar dream possible only for the rich and famous.

As for noise, Scholl said Boom has contracted with Rolls-Royce to design turbofan engines without the loud, gas-guzzling afterburners that plagued the Concorde (the planes, he said, will be net-zero carbon emissions that will fly on sustainable aviation fuel being developed with a blend of biofuels and recycled waste).

But until laws that prohibit overland supersonic flight are changed, Boom will be limited to transoceanic routes. This is where NASA is stepping in to try to open up the market.

“Currently, we have a speed limit in place for commercial airplanes that essentially says you're not allowed to fly faster than the speed of sound, which is about 700 mph,” said Craig Nickol, project manager for NASA’s Low Boom Demonstration Project, a result of the sonic boom created at higher speeds.

Nickol is working to build a quieter supersonic jet with Lockheed Martin called the X-59 QueSST that will enable NASA to collect data for the United Nations International Civil Aviation Organization to show how improvements in aerodynamic design and technology can mute sonic booms. The jet is currently in assembly, and the team is targeting mid-2022 for its first test flight.

“If we can get the speed limit changed to a noise limit, it's our hope that we can open up commercial supersonic overland travel before the end of the decade,” Nickol said.

Scholl points to the rule change as being critical. “Until supersonics are allowed to fly overland, the private jet market won’t be viable,” pointing to Aerion Supersonic, a startup that had struck partnerships for a supersonic business jet with Airbus, then Lockheed, then Boeing before it threw in the towel last month, citing financing issues.

Boom Supersonic remains years from even starting manufacturing. The company plans to break ground on a factory in 2022 at a location yet to be determined and start production in 2023. The first plane is expected to roll off the assembly line in 2025, begin flying in 2026, and then carry passengers by 2029.

In addition to the 15 jets it plans to buy, United has an option for another 35 aircraft, for a total of $10 billion. But it likely doesn’t have to fork over the cash—other than a nonrefundable deposit—until the government clears Boom’s planes to fly.

In addition to United, Japan Airlines has preordered 20 of Boom’s aircraft for $4 billion and Virgin has signed a letter of intent to buy 10 planes for $5 billion.

Investors in Boom, which was founded by Scholl in 2014, include a number of Silicon Valley elite including LinkedIn cofounder Reid Hoffman, billionaire philanthropist Laurene Powell Jobs, and investors Paul Graham, Sam Altman, and Ron Conway.

In addition to providing faster flights, Scholl, a former Groupon and Amazon executive, said he’s striving to make passengers feel more refreshed when they get off the airplane than when they get on. For example, each passenger will get a large seat, set apart from others, with different configurations for reading, relaxing, sleeping, working, and watching movies—a step up from today’s business class, which can be crowded with middle seats. He also emphasized that passengers will have a spectacular view, partly a consequence of the jets flying at 60,000 feet, far higher than today’s commercial airliners.

“When you fly supersonic, the sky is a deeper blue and you can see the curvature of the earth. It’s absolutely breathtaking,” Scholl said.

One thing is for sure: He’s not worried about demand for travel dropping off as a result of the pandemic.

On the contrary, Scholl said, “for decades, pundits believed that telecom was going to kill business travel, and they were wrong every time. Zoom calls make us want to be there more, not less.”