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Supersonic air travel is about to make a resurgence. Several companies—such as Boeing, Lockheed Martin, and the startup Boom Technologies—are developing concept aircraft to cut the time it takes to make a transcontinental trip in half. And instead of taking six hours to fly from New York to Los Angeles, travelers could make the trip in just three. The U.S. Congress is considering rules to permit supersonic flights over land in certain circumstances. Unfortunately, citing potential environmental concerns of yet-to-be-developed aircraft, many environmental activists have started an effort to stop more permissive rules for the technology. If they are successful, they will slow progress in a technology that could bring substantial consumer and economic benefits by speeding up flights.
Those opposing congressional approval of supersonic flights fear that reintroducing supersonic transport aircraft (SSTs) will contribute to more carbon dioxide in the atmosphere, because historically, SSTs have burned more fuel than subsonic alternatives. For example, relying on marketing designs from a single company’s website and fuel efficiency projections from older SST models, the International Council on Clean Transportation (ICCT) released a report that predicted dire environmental consequences that would result due to increased emissions from SSTs. Similarly, Carl Pope, former executive director of the Sierra Club, wrote an article in the New York Times calling for investors to cut ties with supersonic aircraft developers because SSTs could “damage the climate.” Others point to projected ticket prices and call supersonics an environmental carve-out for the rich. As Bill Hemmings, aviation director of the ICCT put it, “Why should a small segment of the population be exempted from the Paris agreement just because they want to travel faster?”
In the past, concerns over environmental impact and noise pollution from groups such as the Anti-Concorde Project in the 1960s and 1970s limited the use of older SSTs, such as the Concorde, halting investment and eventually leading to their decommission. But while the Concorde did have significant problems with fuel efficiency—burning four times as much fuel as a Boeing 747—companies are now rethinking the design of these aircraft and developing new engines to address inefficiencies. Companies are beginning to develop and test advanced supersonic aircraft. For example, Spike Aerospace announced it will start high-speed tests on its demonstrator in mid-2018. Without knowing how these new aircraft are designed or optimized, detractors are putting the cart before the horse (or the aerospace equivalent of that idiom).
There are several reasons to think the re-introduction of SSTs will not have an outsized impact on the environment relative to their subsonic cousins. First, it is in the interest of supersonic aircraft developers to make their planes as fuel efficient as subsonic aircraft because of the volatility of fuel prices. Indeed, soaring fuel prices have pushed U.S. airlines into bankruptcy in the past, and are still having an adverse effect on the industry today. This problem will be even more aggravated for supersonic companies—unless they can offer services roughly as efficient as subsonic flights. For example, at least one supersonic company already claims it can achieve this parity.
Second, even if SSTs remain relatively inefficient, policymakers have already created a backstop to prevent rising emissions across the aviation industry. Traditionally, aviation is one of the hardest industries to decarbonize within the transportation sector because airplanes require fuel with high energy density, which limits the viability of alternatives to fossil fuels, and it currently contributes roughly 2 percent of global emissions. To limit emissions in the aviation industry, the International Civil Aviation Organization (ICAO) created the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) that ensures there will be no net emissions growth from 2020 onward across the entire industry. CORSIA applies to both supersonic and subsonic flights in all major developed countries and will take effect years before any SSTs take flight. Each participating country is responsible for compliance and enforcement, and the Federal Aviation Administration (FAA) plans to work with ICAO when setting rules for future SSTs. In short, this means that any increased emissions created by the introduction of SSTs will need to be offset by more efficiency in other areas within the aviation industry.
If policymakers really want to make air travel more efficient, then they should create permissive rules around the testing and use of supersonic technology. Certain theoretical technologies, such as variable-cycle engines (a hybrid engine that combines the best aspects of turbofan and turbojet engines), could vastly improve the capability and fuel efficiency of SST jet engines. However, companies will not be able to develop these advanced technologies without a substantial amount of R&D. This is a classic chicken-and-egg problem: To generate more investment into supersonic research there must be a market for SSTs, but without permissive rules that allow for supersonic flight there will be no buyers for the technology.
Moreover, just because ticket prices for supersonic travel will be high does not mean policymakers should prevent its development. While new technologies are often first purchased by higher-income individuals, as autos were in the early 20th century, their purchases help create a market and allow companies to improve technologies, generate efficiencies, and create economies of scale. This brings costs down so that more people can afford to use them.
It is important to recognize that this supersonic technology has been on the shelf since the Concorde fleet was retired in 2003, and environmental standards have not kept up with the technology. Where standards for SSTs are outdated or do not exist, policymakers should strive to create new standards. These standards should incorporate consideration of environmental impact and energy efficiency, as well as be technologically feasible, economically reasonable, and flexible enough to respond to new iterations and improvements of the technology. But the lack of standards should not be a reason to halt development or deployment of SSTs.
Fortunately, U.S. policymakers are taking a forward-looking approach to supersonic flight. The Senate will soon take up the FAA Reauthorization Act, which would lift limitations on supersonic travel over land. The bill has already passed in the House of Representatives. Moreover, the FAA is planning to initiate two rulemakings to create a noise certification and special flight authorization for tests of SSTs.
U.S. policymakers should continue down this path to create more permissive and updated rules for SSTs. Only by allowing the technology to achieve lift-off will policymakers be able to spur investment in supersonic technology and improve its efficiency and effectiveness.