The supersonic Concorde of the 1970s was a fabulous aircraft in its day — transporting passengers across the Atlantic in half the time taken by other commercial aircraft, albeit at a cost.

An aeronautical marvel  that made its last flight 16 years ago this week, it still had ecological shortcomings and high operating costs.

Now at a time when carbon emissions and our planet’s well-being are in the spotlight, can a return to commercial supersonic flight really be sustainable, profitable for airlines and manufacturers, and affordable for passengers?

There are two US companies that certainly think so, and they’re going full throttle with plans to bring supersonic airplanes to market by the mid-2020s. The journey times suggested are as short as New York to London in three hours, 15 minutes.

One is targeting airlines, the other the executive jet market, and they’ve both got different solutions to one of the major environmental sticking points of supersonic flight: how to manage the sonic boom.

“Concorde was a brilliant piece of machinery, a noble experiment, but it put too much emissions in the environment, too much noise into our communities, and was too expensive to operate.

“What we’re trying to do is very different,” Tom Vice, chairman, president, and CEO of Aerion Corporation tells CNN.

The firm is developing the 8-12 passenger AS2 supersonic jet at its Reno, Nevada, headquarters.

Compared to regular flights, the AS2, traveling at Mach 1.4 (more than 1,000 mph), promises to shave three and a half hours off the journey from New York to Cape Town, and more than four hours off trips between JFK and Singapore and JFK and Sydney.

Aerion has already secured a launch customer, fractional jet ownership and leasing company Flexjet, with an order for 20 aircraft. The AS2’s first flight is slated for 2024 and the company intends to take the plane to market in 2026.

The AS2 has a price tag of US$120 million, which the planemaker thinks is a price that people will pay because of the time savings.

But Aerion’s ambitions are also for the aircraft to operate benignly in the skies: “The world can’t wait until 2050 to become carbon neutral. We have to do this today,” says Vice.

According to AINonline, partner GE Aviation has stepped up with a program to design and build its Affinity line — the first purpose-built civil supersonic engine platform in 55 years.

Built around the same GE core found on the CFM56 (GE designed it as part of a consortium with Safran), the Affinity will be optimized for efficiency in both subsonic and supersonic flight. Spirit AeroSystems is making the AS2’s pressurized fuselage.

In the cockpit, Honeywell is revolutionizing the flight deck, using its expertise in supersonic military jets to design the AS2’s mission processors, displays, sensors and flight control systems.

The company is also committed to a substantial reforestation program to assure carbon offsets for every customer on every flight.

Then there’s noise.

Vice says that the AS2 is designed to meet Stage 5 Airplane Noise Standards, the most stringent landing and takeoff noise regulations. “We think we’ve solved that problem,” says Vice. “Our aircraft is going to be as quiet as other airplanes around airports.”

But perhaps one of the AS2’s most innovative features is its “boomless cruise” which allows the plane to fly supersonically over land without the boom striking the ground. Instead, the noise gets refracted back up into the atmosphere, CNN reported.

Boom has already garnered US$6 billion worth of pre-orders for 10 Overtures from Virgin Group and 20 from Japan Airlines. Japan’s national airline also invested US$10 million in Boom in 2017. Credit: JAL.

Aerion invented “boomless cruise” because the alternative type of quieter supersonic flight, called “low boom,” while less noisy than Concorde, still produces noise on the ground similar to the rumble of distant thunder.

Vice is keen to prove the new technology can work and “once regulators see that we can do that reliably, we’ll have the first aircraft in history that can fly supersonic over land, and nobody on the ground will hear the boom.”

Vice reckons that “boomless cruise,” coupled with carbon-neutral operations, will deliver compelling productivity advantages for prospective AS2 customers.

Meanwhile, in Denver, Colorado, a 55-75 seater supersonic airliner named Overture is shaping up in the hangar of Boom Supersonic.

The aircraft, designed to cruise at Mach 2.2 (1,451 mph), has a price tag of US$200 million, and has already garnered US$6 billion worth of pre-orders for 10 Overtures from Virgin Group and 20 from Japan Airlines. Japan’s national airline also invested US$10 million in Boom in 2017, CNN reported.

“Overture is moving through the design phase, where its key technologies and specifications are being developed and refined,” Blake Scholl, founder and CEO of Boom Supersonic, tells CNN.

“Many of the key components have already undergone several successful tests, including testing our engines with sustainable alternative fuels. Overture will begin flight testing in the mid-2020s. We’ve already executed successful engine tests using pure biofuel and are designing our aircraft to accommodate alternative fuels.”

Earlier in 2019 the company formed a partnership with Prometheus Fuels, a company that’s using clean energy to make zero-net carbon fuels out of carbon dioxide that is already in the atmosphere.

Regarding noise, Scholl says that the impact of Overture on airport communities will be similar to the quietest aircraft it replaces.

In addition, Overture flights will focus on more than 500 primarily transoceanic routes that benefit from the aircraft’s Mach-2.2 speeds — such as New York to London or San Francisco to Tokyo.

The plan is that Overture will cruise at subsonic over land, meaning no sonic boom will affect populated areas, and cruise supersonically only over water.

Boom Supersonic estimates that by the mid-2020s market demand will require between 1,000 and 2,000 Overture aircraft in the first ten years after it enters service, representing a US$265 billion market.

“Carriers operating Boom’s airliner will be able to offer profitably fares similar to the business-class, long-haul ticket prices seen today,” claims the Boom CEO. “For a one-way trip from New York to London, this means that the airliner can turn a profit at fare levels around $2,500. Our ultimate vision is to reduce operating costs to make supersonic flight even more affordable and accessible.”

As an indication of how supersonic fever is spreading throughout the industry, UTC’s Aerospace Systems reports it has recently invested more than US$100 million in R&D, with a portion dedicated to the areas of noise and high temperatures associated with supersonic flight, AINonline reported.

The company has a history in supersonics, having been one of the suppliers on the Concorde program. UTAS also has experience with some the technologies in subsonic applications, such as its titanium liquid interface bonding process on its fan case for the Rolls-Royce Trent 900.

“We firmly believe that the next big step in aerospace is to go into supersonics,” said Gary Reynolds, UTAS VP of regional and engine systems.

Aerion partner Lockheed Martin is also researching boom effects with its X59 program. That effort was specified in the FAA funding bill, and the research would involve establishing a test range in a remote area where a sample of people would be asked to evaluate sonic booms under varying test conditions — atmospheric and aerodynamic.

Developing the first supersonic business jet is a competitive exercise. “It’s a race,” said one Aerion executive. Spike Aerospace is also developing its program.

Also, some are intrigued that Gulfstream, which had long ago back-burnered its own supersonic development program, recently reserved trademarks on the model names G1100 and G1200, fueling speculation that it could be reviving plans to get back into the Machbuster race.