Fifty years after the first flight of the Anglo-French Concorde, supersonic air travel could be poised to make a comeback. But environmental groups are questioning whether a return to high-speed flight is appropriate with commercial aviation coming under increasing pressure to reduce its emissions.

Boeing’s announcement in February of a “significant investment” in Aerion vaulted the supersonic business-jet developer from struggling startup to serious contender. Of the companies hoping to field a new-generation supersonic transport by the mid-2020sAerion now looks most likely to be first.

On the heels of news that it will provide engineering and manufacturing support for Aerion’s AS2, Spirit AeroSystems, Boeing’s biggest supplier, announced it would design the pressurized fuselage for the Mach 1.6 business jet. Aerion already has GE Aviation onboard, developing the engine, and Honeywell, providing the avionics. More supplier announcements are expected shortly.

Boeing’s investment was a surprise, and its value not disclosed, but its scale can be inferred from the fact that two people on Aerion’s new five-member board are senior Boeing executives. And who they are is revealing: Mike Sinnett, VP-product strategy and future airplane programs at Boeing Commercial Airplanes, and Ken Shaw, VP-supply chain at Boeing Global Services.

Boeing has long worked with NASA on supersonic transport technology, most recently on low-sonic-boom designs, but has shown no inclination in the past few decades to develop its own aircraft. Now it has aligned the Aerion investment under its NeXt business unit, formed to pursue future urban, regional and global mobility initiatives, from air taxis to hypersonic airliners. And Aerion may be starting with a supersonic business jet, but it wants to apply its technology to larger aircraft over time. 

“We are focused on disrupting every segment of aviation with efficient supersonic aircraft,” Aerion CEO Tom Vice says. “We at Aerion, and at Boeing, have continued to study the market, economics and technology required for commercial airliners. I believe it is just going to take time to create a sustainable commercial supersonic airline market.”

Noise rules

Supersonic aircraft need more thrust, with implications for fuel burn, noise and emissions. Aerion’s technology is focused on producing an aircraft that can meet the same Stage 5 landing and takeoff noise limits as newly certified subsonic airliners, while flying as efficiently and cleanly as possible at both supersonic and subsonic speeds. Unlike Denver-based startup Boom Supersonic, Aerion is not pushing for special supersonic noise rules. 

“We have to meet today’s strict regulatory and certification requirements while we also build sustainable supersonic flight that not only the regulatory agencies can accept, but the public will embrace,” Vice explains. “And Aerion airliners—Aerion Boeing airliners—will have to be as environmentally responsible as our business jet.”

The AS2 is not a low-boom design, and Aerion’s business case—like that of Boom for its 55-seat Mach 2.2 Overture airliner—is based on flying supersonically over water, but subsonically over land. But if, as hoped, rules are amended eventually to permit flight above Mach 1 over land, Aerion plans to exploit a phenomenon called Mach cutoff to fly at Mach 1.2 without producing a discernable boom on the ground—a capability it calls boomless cruise.

“We do not advocate the lifting of the restriction on overland supersonic flight without there first being an acceptable technical and operational approach that attenuates the noise generated by the sonic boom,” Vice says. “We actively oppose any company that takes an irresponsible approach to the elimination of Mach 1 overflight restrictions.” 

Vice believes there are only two valid approaches that will lead to supersonic flight over land: low boom and no boom. “I think it will take decades for [low-boom] technology to find its way into production aircraft,” he says. “I believe boomless cruise will be the first operational capability that will reliably achieve supersonic flight over the US that the regulator will accept and the public will embrace.” 

Europe already is lining up against the US to oppose any relaxing of noise rules to enable a renaissance of supersonic flights, and there are no such aircraft programs active on the continent. Environmental groups also are painting dire pictures of the noise and emission impacts—assessments Boom disputes.

Ensuring supersonic transports return to stay will require more than just high speed. The AS2 “provides the first environmentally responsible platform that can begin a long, sustainable design cycle that will allow us to grow in speed responsibly,” Vice says. 

Boeing’s backing suggests the commercial aircraft giant believes Aerion is on the right track to a sustainable return of supersonic air travel.