One Giant Leap Backward: The Restriction of Overland Supersonic Aviation

The above statement encapsulates the purpose and complexity of the federal government’s transportation policy. While it renders the aim of the policy clear, the application of and means to achieve its purpose are significantly muddled—perhaps nowhere more so than in the regulatory structure governing civil supersonic transportation.

The advent of supersonic transportation, namely Concorde, in 1969 heralded the arrival of a new and glimmering aviation age, vast technological improvements (many of which are only now becoming commonplace on new aircraft), and unrivaled speed in civil aviation. Concorde even boasted a sterling safety record until its only fatal accident in 2000. The development imperative of “fast” and “convenient” transportation technology, in the end, however, yielded to an overly broad regulatory structure with a focus on “efficient use and conservation of resources.”

Advances in supersonic transportation came at an incredible financial cost to not only the manufacturing consortium of Concorde, but also the only two nations that would finance and ultimately purchase Concorde, France and Britain. Despite this, Concorde displayed financial viability for the majority of its life span. A tragic accident, rising fuel costs, and the aftermath of the 9/11 terrorist attacks forced the fleet into an early retirement. Since then, an overly broad regulatory structure, which essentially imposes a de facto ban on all civil supersonic air travel by prohibiting the cause of an unwanted effect, rather than the effect itself, has been in place. Meanwhile, technology has advanced to such a degree that the initial unwanted effect has been left in obsolescence. Impediments to the successful deployment of a new generation of civil supersonic aircraft, therefore, include not only the regulations in 14 C.F.R. part 91 (applicable to all civil aircraft operations in US airspace), but also an outdated and mismatched intellectual property rights structure that rewards second, third, or fourth movers instead of protecting the trailblazer’s investment in this technology.

Concorde

Any discussion of civil, supersonic aviation cannot be had without a brief introduction to, and history of, Concorde. In 1969 Concorde took its first flight, ushering in an unrivaled 27-year era of glamorous, fast, and luxurious jet-setting. “The sense of status, enthusiasm and romance surrounding supersonic airline travel has never stopped.” Concorde represented the culmination of a multibillion-dollar joint venture between Britain and France that gave us aviation technology that is only now, 60 years later, becoming commonplace on aircraft.

The attendant sonic boom (discussed below) prompted most airlines to cancel their purchase options, leaving the Franco-British group with their flag carriers as the only two customers: British Airways and Air France. As this was then-new technology, near hysteria ensued over the intrusive noise. Protests were convened at nearly every major city on Concorde’s inaugural press tour. “Drive-ins” attempting to disrupt all passenger travel at New York’s John F. Kennedy Airport (JFK) were staged. Some in the scientific-environmental community claimed that emissions at Concorde’s flight level would be the proximate cause for the melting of the polar ice caps. A Scottish woman even blamed her unwanted pregnancy on Concorde’s supersonic testing, which she claimed interrupted her rhythm method of contraception. However, when Concorde was flown into JFK, it proved to be nowhere near the sonic cataclysm that was feared, silencing the protestors. Nevertheless, because of its sonic boom, Concorde was limited to trans-Atlantic routes between Washington, New York, Paris, and London for the remainder of its active life span.

Concorde was retired in October 2003, in the wake of a deadly crash three years earlier, and with it ended the period of commercial supersonic flight, the fastest means of traveling the world to date. Though Concorde’s tenure was more limited than may other aircraft types, the absence of a replacement is largely due to a regulatory scheme that prevents overland supersonic flight.

The Problem

The acoustic event that occurs when an object accelerates past the speed of sound is commonly known as the “sonic boom.” “Supersonic-capable aircraft passing Mach 1 produce a loud sound called a sonic boom. Thunder-like sonic booms are caused by air molecules being crowded into shockwaves by an aircraft travelling supersonically. The sonic boom is the ‘wake’ of the plane’s shockwaves combined together, similar to a boat’s wake. Double booms are sometimes produced first by shockwaves from the plane’s nose and then from its tail.” Occasionally, a sonic boom has been severe enough to cause physical damage when it reaches the ground. It is the single most prohibitive aspect of overland supersonic flight. While this claim is somewhat of an outlier, there have been other legitimate claims leveled at operators and the government. The mere testing of supersonic overland flight in the United States has led to litigation involving takings claims under the theories of trespass, nuisance, and inverse condemnation.

Traditional sonic booms were tested for public reaction in Oklahoma City in 1964 for potential supersonic overflight:

The sonic boom test program at Oklahoma City was designed to determine the public acceptability and the effect on ground structures on booms anticipated from future supersonic transport flights, inasmuch as the projected supersonic transport would travel at faster-than-sound speeds, carrying paying passengers, and fly over people and population centers.

The results did not bode well for the possibility of overland supersonic travel and resulted in several rounds of lawsuits against the federal government, though they were ultimately unsuccessful.

Concorde’s Derivative Technology

Due to the unique operational environment and mission objectives, Concorde was forced to be lighter, more powerful, more advanced, more luxurious, and faster than any civil aircraft of its time. In designing something so advanced, a virtual treasure trove of derivative technology was introduced, fomented, or completed. Fly-by-wire control surfaces transmitted pilot inputs electronically to hydraulically operated control surfaces that could operate at speeds in excess of Mach 2. Computer-controlled air intakes that could decelerate air from 1,000 mph to zero mph within the span of 14 feet were the first of their kind within the industry. Advanced braking technology, engine management, and in-flight entertainment are only a few of the advancements brought about by the supersonic efforts of the 1960s. For example, the first fly-by-wire aircraft system, created in the 1960s, is now incorporated into modern, clean-sheet designs.

The disincentive to aggressively invest in research of these technologies due to the absence of standard-setting regulations and the moratorium on supersonic overland flight has impeded advances. Such regulatory decisions may have long-term, adverse technological, political, and social impacts for the United States.

Federal Policy

Federal law controls the pace at which aviation technology is implemented. Well-established policy encourages innovation in air travel for private, commercial, and military aims. Yet environmental concerns, addressing counterbalancing policy, have at times slowed progress and, in reality, America’s prominence in the development of cutting-edge jet technology. The law as it has developed is in tension with clearly stated federal policy goals, as well as commonsense and commercial goals.

The regulatory ban on civil supersonic flights over land is contradicted by a national policy to develop increasingly fast and efficient aircraft—a policy statutorily expressed by Congress:

“The national objectives of . . . the United States require the development of transportation policies and programs that contribute to providing fast, . . . efficient, and convenient transportation.” The statute continues by stating that the purpose of the “Department of Transportation is necessary in the public interest and to— . . . make easier the development and improvement of coordinated transportation service to be provided by private enterprise to the greatest extent feasible; . . . [and] stimulate technological advances in transportation, through research and development. . . .”

Over the years, presidential administrations similarly have emphasized policies encouraging the development of supersonic flight to ensure speed and efficiency for both civilian and military purposes. For example, during an address to graduates of the US Air Force Academy delivered early on in the Jet Age, President John F. Kennedy remarked as follows:

I am announcing today that the United States will commit itself to an important new program in civilian aviation. Civilian aviation, long both the beneficiary and the benefactor of military aviation, is of necessity equally dynamic. Neither the economics nor the politics of international air competition permits us to stand still in this area. Today the challenging new frontier in commercial aviation and in military aviation is a frontier already crossed by the military-supersonic flight.

[It] is my judgment that this Government should immediately commence a new program in partnership with private industry to develop at the earliest practical date the prototype of a commercially successful supersonic transport superior to that being built in any other country of the world.

Sixty years later, however, the United States has yet to produce a viable supersonic transport, despite the advancements in engineering and technology witnessed by the past decades. Additionally, five years after Kennedy’s address at the Air Force Academy, President Lyndon B. Johnson signed into law a congressional amendment to the Federal Aviation Act of 1958, giving unilateral authority to the Federal Aviation Administration (FAA) to ban overland supersonic flight. Additional regulatory complexity was added when the statute was further amended to require US Environmental Protection Agency (EPA) consultation before FAA issuance of regulations regarding sonic booms, and to provide the EPA with joint authority for proposing such regulations.

In March 1973, the FAA issued regulations banning overland civilian supersonic operations in US airspace. This regulatory death knell was written into the Code of Federal Regulations:

(a) No person may operate a civil aircraft in the United States at a true flight Mach number greater than 1 except in compliance with conditions and limitations in an authorization to exceed Mach 1 issued to the operator in accordance with § 91.818.

(b) In addition, no person may operate a civil aircraft for which the maximum operating limit speed MM0 exceeds a Mach number of 1, to or from an airport in the United States, unless—

(1) Information available to the flight crew includes flight limitations that ensure that flights entering or leaving the United States will not cause a sonic boom to reach the surface within the United States; and

(2) The operator complies with the flight limitations prescribed in paragraph (b)(1) of this section or complies with conditions and limitations in an authorization to exceed Mach 1 issued in accordance with § 91.818.

14 C.F.R. § 91.817. Thus, no civil supersonic aircraft have flown in the United States since Concorde; and even when Concorde did operate in US airspace, it was prohibited from producing sonic booms over land.

The FAA’s prioritization of noise abatement and environmental issues over supersonic flight was again reiterated in its October 16, 2008, Statement of Policy, which stated “that any future supersonic airplane [may] produce no greater noise impact on a community than a subsonic airplane.” The 2008 Policy Statement further stated, “Public involvement will be essential in defining an acceptable sonic boom requirement, and public participation would be part of any potential rulemaking process.”

The 2008 Policy Statement was nevertheless careful to note a change from the 1973 ban on supersonic flight over land. It noted the noise levels for certification of aircraft were modified in 1994 and in 2005, underscoring the federal government’s ability to evolve on the issue of noise abatement.

Nevertheless, existing regulations, especially part 91 in title 14 of the Code of Federal Regulations, continue to inhibit the reality of future supersonic flight. The regulations further discourage private companies (with a few notable exceptions discussed below) from moving forward with research, due to a perception that such investment is unlikely to result in a successful process to gain authorization for supersonic overland flight. This process acts as a de facto prohibition in addition to the regulatory prohibition. Under the regulatory scheme, even an overland flight with an imperceptible and trivial sonic boom signature (a reality today due to technological advancements) is currently banned, even though such a flight has no adverse impact on persons below or to the environment.

In 2021, part 91 was amended by a final rule titled “Special Flight Authorizations for Supersonic Aircraft.” The change was largely organizational in nature; it simply moved Appendix B to the body of the regulation in part 91. One notable change, however, was the addition of noise testing as a stated basis for obtaining permission for supersonic flight. Nevertheless, the de minimis impact of the 2021 changes is reiterated within the rule itself, which states, “This rule does not introduce any new FAA policy or change the intent of the original application process” for supersonic flight. “Neither this final rule nor the part 36 noise limit . . . alters the general prohibition on supersonic flight over land. . . .”

State Regulation

Airport noise is controlled by a curious mix of local and federal interests. For example, a local regulation prohibiting the wholesale operation of jet aircraft at an airport for noise concerns was deemed unconstitutional under the equal protection clause in Santa Monica Airport Ass’n v. Santa Monica. However, in that same case, regulations restricting jet aircraft at certain times and under specific circumstances were deemed valid on appeal—the aviation equivalent of a time, place, and manner regulation.

The issues with Concorde’s landing and takeoff profile and potential noncompliance with local regulations at JFK and Dulles were easily overcome by manipulating glide and approach paths and through pilot skill. While airport noise control must necessarily be part of any supersonic flight discussion, it is more easily overcome by planning. Additionally, technological advancements, such as the variable cycle engine, will greatly diminish local noise.

In British Airways Board v. Port Authority of New York & New Jersey, a suit brought about by Concorde’s operation into New York’s JFK and that predated Airport Noise and Capacity Act of 1990 (ANCA)(discussed below), the US Court of Appeals for the Second Circuit observed that “both the vital importance of the aviation industry to the national economy and basic considerations of fairness . . . require[] that even the appearance of whim and caprice be eliminated from critical decisions concerning airport access.” The court went on to explain:

If ever there was a case in which a major technological advance was in imminent danger of being studied into obsolescence, this is it. There comes a time when relegating the solution of an issue to the indefinite future can so sap petitioners of hope and resources that a failure to resolve the issue within a reasonable period is tantamount to refusing to address it at all.

The appeals court affirmed the district court’s order enjoining any prohibition of Concorde operations at JFK. It did, however, encourage promulgation of “reasonable, nonarbitrary, and nondiscriminatory noise regulation that all aircraft are afforded an equal opportunity to meet.”

Following the passage of ANCA, airport noise and access restrictions are subject to a robust federal regulatory scheme set forth at 14 C.F.R. part 161, with the FAA charged with determining whether such restrictions are permissible under ANCA. Nevertheless, equal protection and commerce clause considerations, which proved central to the decisions in Santa Monica Airport Ass’n and British Airways Board, are readily apparent in ANCA and its implementing regulations at part 161. Although ANCA brought greater predictability and uniformity to disputes based on airport noise and access restrictions, the law did not alter the regulatory scheme applicable to supersonic aircraft. Indeed, Concorde continued operations to and from the US for nearly 13 years after the passage of ANCA, during which time the aircraft produced sonic boom while over the ocean only, and not land. Regardless, any future local attempts to limit airport access for supersonic aircraft specifically would, in all likelihood, be prohibited under ANCA and part 161.

More Sonic—Less Boom

The current scientific context in which the regulatory ban exists is quite changed from that of over a half century ago when Concorde was being developed and first flew. Advancements in avionics, computer-aided design, and aerodynamic engineering have greatly diminished the drawbacks of supersonic travel, including the sonic boom. We have the engineering technology to begin a new era of quiet, supersonic flight.

For example, a partnership between Gulfstream Aerospace Corporation and the National Aeronautics and Space Administration (NASA) has made significant gains in the suppression of sonic shock waves. This patented technology, called Quiet Spike, utilizes “a multi-segmented articulating boom that, when fully extended from the nose of a supersonic low-boom shaped aircraft, is expected to reduce the effects of sonic booms.” The retractable boom on the front of the aircraft is used to disrupt the standard sonic shock wave and produce a much-diminished noise signature. In supersonic testing, the Quiet Spike resulted in a more rounded pressure waves that resulted in a softer sound which is 10,000 times quieter than Concorde. The vast regulatory criteria in this undertaking are described as a main reason for the Quiet Spike venture:

These tests are just a few in a series of activities which must be undertaken to prove to numerous regulatory agencies and environmental groups, both at home and abroad, that supersonic flight over land is achievable in a way that will significantly reduce the impact of the sonic boom on people and on the environment. It is only one step, but a very important step, for all of us.

Boom Supersonic’s Overture platform is likely the next bearer of the passenger supersonic mantle. It has proven to be the most viable, even garnering orders from United Airlines, American Airlines, and Japan Airlines. However, under the current regulatory regime, even the Overture, like Concorde, will be relegated to overseas routes, at least at supersonic speeds.

Additionally, advances in computer-aided design (CAD) have completely redefined the “clean-sheet” design process from that which was available during Concorde’s design years in the 1960s. This is evident in aircraft that easily cruise just below the speed of sound as well as sonic experiments such as NASA’s Shaped Sonic Boom Demonstration. In this experiment, the shape of the fuselage of the supersonic aircraft was subtly manipulated to shape the accompanying sonic boom. This resulted in an extreme reduction in sonic boom perception.

Without a change in the regulation that bans civil supersonic flight over land, though, the market value of any supersonic civil aircraft design is diminished by the operational constraints.

Economic Impediments to Further Advances

Given achievements in the field of nonintrusive supersonic technology and the promise of future technological advances, why is overland supersonic flight not a reality? Why has no entity, public or private, undertaken to gain FAA authorization under part 91?

The answer lies in the regulatory process for gaining supersonic overland flight permissions, which is time intensive and costly, with no guarantee of approval. These regulations stand as a constructive prohibition by limiting the first-mover advantages of a firm undertaking the authorization process. “Even if a particular company thinks that it can persuade Congress to change the rules, subsequent entrants may be able to free ride on that benefit.”

The lack of protection via patents or other intellectual or legal mechanisms for the first mover further inhibits market entry. The technology of supersonic travel is not only prolific but it is obvious, rendering it difficult to protect under traditional intellectual property rules. There is an element of “social usefulness” that is being ignored by the regulatory and de facto bans on overland supersonic travel. This “orphan business model” is further explained:

Orphan business models may also merit property rights protection where the principal obstacle to development is that government regulation may impede progress. To succeed both technologically and legally, the prospective developer of a jet design that would reduce sonic booms must persuade Congress or the Federal Aviation Administration to permit certain types of supersonic jet aircraft. The problem is that given such success, other jet designers may invent other forms of sonic boom reduction technology and free ride on the lobbying effort of the first manufacturer.

Gulfstream owns a patent on its Quiet Spike. However, its executives say that “[i]n order to make the market viable for supersonics you have to make it feasible to fly overland faster than sound—which is currently against the law. We don’t think there is a viable market until you change [the law].” Gulfstream, and likely other similarly situated companies, are reluctant to expend the vast amounts of money and time, in addition to research and development, on lobbying and testing to receive authorization for overland supersonic travel.

First-Mover Advantage Protections

This “social inefficiency” must be mitigated by some kind of intellectual property scheme that preserves and protects the first-mover advantages earned by any such authorization. One such approach could be granting an exclusive right to sell supersonic aircraft for a specific amount of time to the first mover. Another would be a wholesale government initiative, specifically targeted to encourage and reward supersonic advances. Third, a consortium (similar to that behind Concorde) may prove effective to overcome the regulatory barriers. These comport with Congress’s statutory directive to the US Department of Transportation (including the FAA) to “stimulate technological advances in transportation, through research and development or otherwise,” and ease “the development and improvement of coordinated transportation service to be provided by private enterprise to the greatest extent feasible.”

Conclusion

In the words of Gulfstream’s senior vice president,

The regulation was rightfully initiated as a reaction to the potential dramatically increased noise levels due to sonic booms. However, since then, advances in technology have enabled us to produce aircraft that are much quieter. We believe it is time to consider reviewing and amending the regulations to ensure they reflect current technologies, which have brought us to the threshold of revolutionizing aviation as we know it today.

Though the prohibition on supersonic travel once justifiably was used for noise abatement, the advancements in technology and research surrounding shaped sonic booms have rendered the prohibition unnecessary. The complex web of FAA and EPA restrictions and other requirements exponentially increases the barrier to entry for any manufacturer wishing to invest in the research and development of a supersonic aircraft. This already high barrier is exacerbated by the lack of an intellectual property structure that would protect the first mover instead of incentivizing subsequent movers into the market.

Famed petrolhead and provocateur Jeremy Clarkson famously lamented:

Now Concorde is grounded, it becomes a museum piece like no other. Because, unlike steam trains or Ford Mustangs, there is nothing that has superseded it. We’re not looking at Concorde as an example of outdated technology. It is still at the cutting edge. Losing it has been one giant leap backwards for mankind.