United Airlines Wants To Bring Back Supersonic Air Travel. Will the FAA Let It?

The company has agreed to purchase 15 supersonic airliners from Denver-based aerospace startup Boom.

Interest in the return of commercial supersonic air travel is booming. But will the technology be able to break through the regulatory barriers that stand in its way?

On Thursday, United Airlines announced its intention to purchase 15 supersonic Overture jets from Denver-based aerospace startup Boom Supersonic. The hope is for these 65–88-person airliners—which have yet to be built, let alone tested—to be ferrying passengers across oceanic routes by 2029, according to a joint press release put out by the two companies.

"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," said Boom CEO Blake Scholl.

On its website, Boom says a trip from San Francisco to Tokyo on its Overture jet will take six hours, instead of the current journey of just over 10.

Faster-than-sound travel isn't a new technology. Chuck Yeager broke the sound barrier in 1947. But commercial airline passengers have been stuck at subsonic speeds ever since the supersonic Concorde plane was taken out of service in 2003.

A fatal crash in 2000 and its noisy, fuel-hungry engines helped do that airliner in. Not helping its chances of success was a 1973-issued Federal Aviation Administration (FAA) regulation banning supersonic flights over land, meaning it could only offer transatlantic flights.

Since the Concorde's retirement, there have been a number of economic and technological developments that make profitable supersonic travel more feasible, says Eli Dourado, a senior research fellow at Utah State University's Center for Growth and Opportunity (and former global policy chief for Boom).

"On a technological level there is no reason that an aircraft could not be much, much better than what Concorde was able to achieve," Dourado tells Reason.

Improved materials are one reason, he says. The aluminum that the Concorde was built with would expand thanks to the high heat of supersonic travel, creating additional drag and introducing a complicated engineering problem of keeping its nonexpanding cabin airtight. Newer carbon fiber materials are more thermally stable and easier to shape into the curves needed for supersonic flight.

Advances in software have also enabled engineers to test new designs much more rapidly.

"When Concorde was developed, they basically did it with pencil and paper. They did it with slide rules and drafting tables," says Dourado, meaning it would take months to test new designs. Today's computer simulations allow you to "test thousands of designs over the life of an aircraft program, instead of ten or so that Concorde was able to do."

Lastly, 50 years of advances in lighter, fuel-efficient engines also make supersonic flight cheaper and thus more commercially viable. The rapid growth in the market for premium transatlantic flights also improves the economics of the industry.

Coupled with these technological changes are a few more marginal updates to federal supersonic regulations.

In January 2021, the FAA finalized new rules making it easier for companies to get permission to conduct supersonic test flights over land. It's also currently in the process of crafting new noise standards for supersonic aircraft during takeoffs and landings.

Both those regulatory changes were required by a reauthorization of the FAA that Congress passed in 2018. That law also directs the agency to review its existing ban on routine supersonic flights once every two years.

One shouldn't expect revocation of that rule in the near future, however. Before the FAA can ditch that prohibition, the National Environmental Policy Act requires it to first perform a review of the environmental impacts (including noise effects) of supersonic flight.

That, in turn, requires data on those noise effects that the FAA doesn't currently have. A NASA program to conduct test flights of "quiet" supersonic aircraft over communities is supposed to provide the information the FAA will need to conduct its environmental review, but the completion of that program is still years away.

"It is good that the FAA has been easing its very strict prohibitions on even testing overland [flights]," says Marc Scribner, a senior transportation policy analyst at Reason Foundation, the nonprofit that publishes this website.

That gives United and Boom the breathing room they need to test their new technology and potentially put it into service over oceanic routes where supersonic flight is still allowed.

Should that prove successful, it'll hopefully pave the way for broader legalization of supersonic flight across the U.S. as well. "Before you have an actual, in-service aircraft it's going to be difficult for regulators, the public, and politicians to get fully behind overland supersonic," says Scribner.

At the same time, he cautions that traditional "not in my backyard" (NIMBY) complaints about aircraft noise as well as environmental concerns about the emissions from air travel could lead to additional barriers for the industry.

"I think that's why you saw in the United announcement, that [its supersonic jets] would be fueled by 100 percent sustainable aviation fuel," he says. "That was in part trying to get out ahead of objections or concerns we've heard expressed from some environmental groups about these technologies."

Boom's plan is to start test flights of its Overture planes by 2026.