Thus, with high-performance aircraft, the altitude Mach number is usually given, as supersonic flight at sea level is rare: It entails vastly greater stresses on the airframe and makes pilot margin of error virtually zero. Put simply, unless you are a member of the Navy Blue Angels or Air Force Thunderbirds, fuhgeddaboudit.
Surprise flight fact of the week: The first airplane to be used in testing stresses encountered in transonic flight was a late model Spitfire, in 1943. The upgraded Spitfire used a turbocharger that compressed extra air so that the engine could operate at higher speeds; the result was a plane that flew at 40,000 feet and attained top speed in level flight of 420 mph — a 10,000-foot and 70-mph gain over earlier models. Pushed into a dive at 40,000 feet, at 25,000 feet the plane had topped Mach 0.9 — about 600 mph — faster than commercial jetliners fly today in level flight. In 1952, it reached 690 mph in a dive. Yet it only reached Mach 0.94, because this was below 35,000 feet at the end, and its speed was computed against sea-level Mach. Subsonic aircraft can exceed the ground speed of sound in level flight, given a strong tailwind, without breaking the sound barrier. This is because the speed of sound is calculated against airspeed. A plane going 600 mph with a 200 mph tailwind flies faster than sound travels at ground level but does not break the sound barrier in flight as its airspeed nets out at 600 mph. Thus, in Feb. 2019, a Virgin Atlantic 787 Dreamliner hit 801 mph in level flight, going its normal 561-mph cruising speed but carried by at 240-mph tailwind.
When Chuck Yeager became the first to break the sound barrier on Oct. 14, 1947, he did so having been dropped from a B-29 mother ship and using Bell X-1’s rocket engine. Sustained, level supersonic flight required airframe redesign and also a redesigned jet engine, then several years away. Yeager’s triumph was followed by the first Mach 2 jet flight in 1953 and the first Mach 3 jet flight in 1956. The all-comers record was set by a rocket plane, the X-15, in 1967. It attained hypersonic speed — defined as (altitude) Mach 5 and higher — in level powered flight, Mach 6.7 (4,520 mph). In 1963, the X-15 set the high-altitude mark at 67 miles (354,200 feet).
The first jet to exceed the speed of sound in fully powered level flight (no mother ship) was the North American F-100 Super Sabre, in 1953. But the future was prefigured by the British military’s Fairey Delta 2 (FD2). In 1956, the FD2 shattered the F-100’s best performance of 822 mph, made in 1955, hitting 1,132 mph, nearly half a Mach number faster. This was made possible by the FD2’s revolutionary delta-wing configuration. Designers adopted the delta-wing concept as Concorde began to take shape in the late 1950s.
The Concorde offered bucket seats, akin to those in a sports car, and little overhead space, but separate boarding facilities and luggage unloaded in 10 minutes made up for less luxury seating and storage. With a peak speed of Mach 2.2 (1,450 mph), the Concorde traversed the Atlantic Ocean in 3.25 hours flying eastward, and 3.75 hours flying westward. The air distance was 3,450 miles from New York to London, and 3,635 miles from New York to Paris. Thus, Concorde cut four hours off of transatlantic flight time flying westward and three hours flying eastward. Its record for the fastest New York-to-London flight, set Feb. 7, 1996, was 2 hours, 52 minutes, and 59 seconds. The London-to-New York City record was set on Dec. 16, 1979, at 2 hours, 59 minutes, and 36 seconds.
Concorde’s higher-altitude flight path virtually neutralized the winds of the East-West Jet Stream, whose winds are far faster at 30,000 to 40,000 feet than at Concorde’s 50,000 to 60,000 feet — a stiff headwind can easily add an hour to a subsonic jet’s flight time, whereas Concorde would lose only 10 minutes — thus, Concorde’s routes were always the shortest, without regard to the Jet Stream, whereas subsonic routes vary in order to avoid headwinds or ride tailwinds.
Concorde destinations initially numbered more than the regular service across the Atlantic. In addition to scheduled destinations, Concorde was used for thousands of charter flights, including aerial circumnavigations. The fastest westward was a 1992 Lisbon-to-Lisbon flight westward, which took 32 hours, 49 minutes, and 3 seconds, 23 hours and 7 minutes in flight. It made six refueling stops; passengers never saw the setting sun. The eastward record was a 1995 charter flight from New York with six stops, which took 31 hours, 27 minutes, and 49 seconds.
The as-yet unsolved problem of quieting the sonic boom was of course a huge limitation on supersonic air travel, barring supersonic travel over land.
Another key factor limiting Concorde’s viability was range. The maximum range achieved by Concorde was 4,500 miles. Apply this to BA’s brief offering of service from London to Rio de Janeiro, using figures rounded to the nearest hundred miles. The direct air distance is 5,800 miles, a 10.25-hour flight by scheduled subsonic jet. Concorde needed two stops for refueling. The first leg, London to Washington, D.C., is 3,700 miles. The second, Washington to Miami, is 900 miles. The final leg, Miami to Rio, is 4,200 miles, for a total of 8,800 miles. The middle leg is far too short for Concorde to attain Mach 2 cruise; reaching Mach 1 then took 15 minutes with another 15 minutes needed to decelerate. Thus, only a brief flight time at Mach 1 would be possible, at most one hour faster than the two hours at subsonic speed. Add in the 300 extra air miles flown due to the Miami stop — at Mach 1, 25 minutes. Then add two stops to refuel (pump time plus two-way tarmac taxi), making 45 minutes per stop. Finally, add two more accelerations and decelerations and it was a travel time wash — assuming no bad weather at Concorde’s extra stops.
America was interested, needless to say, in developing a leapfrog Mach 3 SST. Faced with the Concorde’s head start, the U.S. would build a larger, faster aircraft — in effect, it would leapfrog the British-French design. The U.S. had a head start on Mach 3 aircraft, having built the only two Mach 3 aircraft — the SR-71 Blackbird and XB-70 Valkyrie — capable of sustained Mach 3-level flight.
In June 1963, President John F. Kennedy, the day before announcing that the U.S. would develop an SST, made a furious phone call to Treasury Secretary C. Douglas Dillon over Pan Am Chairman Juan Trippe’s having jumped the gun by publicly announcing his apparent intention to purchase Concordes. Trippe was dissuaded by JFK from pursuing his option in favor of buying American, if the American SST project came to fruition.
JFK formally declared in favor of the SST in his June 5, 1963, commencement address at the U.S. Air Force Academy. He did so in the context of a broader challenge for military and civil aviation, saying:
For some of you will travel where no man has ever traveled before. Some of you will fly the fastest planes that have ever been built, reach the highest altitudes that man has ever gone to, and lift the heaviest payloads of any aviator in history.… [And] some of you will help develop new planes that spread their wings in flight, detect other planes at an unheard of distance, deliver new weapons with unprecedented accuracy, and survey the ground from incredible heights as a testament to our strong faith in the future of air power and the manned airplane.
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….
Having reviewed their recommendations, 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. An open, preliminary design competition will be initiated immediately among American airframe and powerplant manufacturers with a more detailed design phase to follow. If these initial phases do not produce an aircraft capable of transporting people and goods safely, swiftly, and at prices the traveler can afford and the airlines find profitable, we shall not go further.
In 1964, President Lyndon B. Johnson formally authorized the SST project. He issued Executive Order 11149, establishing the President’s Advisory Committee on Supersonic Transport. The executive order stressed LBJ’s overriding concern about cost, requiring that the committee coordinate with the Bureau of the Budget (predecessor to the Office of Management and Budget). In an ironic twist of fate, the executive order was issued April 1, 1964 — April Fools’ Day. SST opponents would enjoy the last laugh.
A Boeing design concept was approved by President Johnson towards the end of 1966: At 318 feet, it was then the longest airframe ever built — half again as long as Concorde’s 200 feet. At 300 passengers, nearly thrice Concorde’s 100 (standard configuration; charters would squeeze in 128 by narrowing legroom), its 675,000-pound fully loaded take-off weight was to be 65 percent greater than Concorde’s 408,000 pounds. At Mach 2.7 (1,800 mph) and with a 70,000-foot ceiling, it would be 25 percent faster, with a ceiling 10,000 feet higher. But its range was identical to Concorde, thus limiting its prospective speed advantage. With variable-geometry wings, it would perform optimally at low, middle, and high speeds, unlike the fixed delta-wing Concorde. Boeing later submitted a delta-wing design when its original idea failed, but it was too late. In 1971, environmentalist groups successfully lobbied the Congress to cancel the entire project.
Their TU-144 — dubbed by wags as the Concordski — looked like a knock-off of Concorde, but in fact this was not true. There was — see link below — actual espionage on the part of the Soviets to aid the TU-144, but this does not alter the differences in design that made the TU-144 much more than a Concorde with Russian lettering on its fuselage. Key differences were stabilizer design, center of gravity, air intakes, wing design, and engine placement. The Soviets falsely claimed that 200 TU-144s were to be produced; in fact, only 16 flyable planes were.
The TU-144 aimed to carry 121 passengers at Mach 2.35 (1,550 mph), a mere seven percent faster. Her maiden flight was Dec. 31, 1968, months ahead of her European rival, and she also passed Mach 1 and Mach 2 milestones months ahead. But the TU-144 crashed at the 1973 Paris Air Show, making it non-marketable as a commercial airliner outside Russia; a second crash of a newer model in 1978 was icing on the cake. It ultimately cruised between 50,000 and 60,000 feet at Mach 2.05 (1,350 mph) — instead of, as originally planned, being 100 mph faster than Concorde, it was 100 mph slower.
This TU-144 site has superb photos, and, in addition, it notes other problems: Its range was 4,000 miles vs. Concorde’s 4,500; it had to use afterburners to boost thrust throughout the flight; and its engines and air-conditioning were so noisy that passengers could only communicate by passing notes. Another TU-144 site offers more: Of 102 flights, only 55 were commercial; in Dec. 1975, it entered service as a mail carrier between Moscow and Almaty, the capital of Kazakhstan, a 2,000-mile flight. Aeroflot began commercial service Nov. 1977 and ended service June 1, 1978, after the May 1978 crash. A longer-range, faster model, TU-144D, carried cargo between Moscow and Khabarovsk, Siberia, a 3,800-mile flight. All service ended June 1, 1983.
In 1974, CBS 60 Minutes aired a segment suggesting that the time for Concorde might have passed. Titled “The $2.5 Billion Misunderstanding,” the project seemed on the verge of cancellation. In addition to the above-referenced spying by the Soviets, the program traced the history of Concorde development since the late 1950s. The segment mentioned soaring costs, driven in part by ferocious environmental group opposition; alarmists predicted that England’s green fields would die, that seagulls and stewardesses would become sterile, and that England’s medieval cathedrals would see their stained-glass windows shattered by sonic booms — and eventually the cathedrals themselves would crumble. Also, the 1973 OPEC oil embargo sent petrol prices soaring, triggering a global recession. Though Concorde was saved, only 12 of the planned 100 planes entered commercial service.
After entering the pilot and passenger nirvana of vibration-free flight, a new monster rears its ugly head: heat. The Concorde aluminum airframe can safely withstand Mach 2. Mach 3 flight requires titanium alloys, far more rare and hence far more expensive. Another reason: The time saved by going from Mach 2 to Mach 3 is far less than going from high subsonic to Mach 2. A New York-to-London flight on an airliner cruising at Mach 3 would arrive only 40 minutes before Concorde, and at vastly higher cost.
For New York to Los Angeles, whose 2,450 air miles are 1,000 miles shorter, a Mach 2 SST would save at most only 30 minutes. For Mach 3 to be a true time saver, flights would have to be much longer. As of 2022, the world’s longest direct flight is New York to Singapore, 8,800 miles, lasting 18.25 hours. At Mach 2, 2.5 times subsonic speed, a flyer saves 7 hours (40 percent of cruising time); at Mach 3, the saving over Mach 2 is another 2 hours. Savings shrink as speed increases: Mach 4 is one-third faster than Mach 3; Mach 5 is one-fourth faster than Mach 4, etc. Thus Mach 2 saves lots of time, Mach 3 a modest added saving, and any faster saves little. Weighed against the higher costs of building faster airplanes with more expensive materials, it looks very dicey.
The U.S. SST effort ended in May 1971. In addition to troublesome technical challenges, the growing power of environmental groups proved a critical factor. In 1966, the noise abatement goal for an SST was to be comparable to the jetliners then extant. But in the late 1960s, new commercial wide-body designs appeared, with engines much quieter than the earlier generation of jets. Their noise level was instantly adopted by the Greens as the revised standard for the SST. (READ MORE from John C. Wohlstetter: Torquemada Airways: Flying Today’s Unfriendly Skies)
According to The Concorde Story, authored by one of the original British Airways Concorde pilots, Concorde’s design and flight endurance made possible continued service until as late as 2020. But the year 2000 was to see the beginning of the end, with the tragic July 25 crash of an Air France Concorde — in a bizarre coincidence, it was the same plane that was used in the film Concorde … Airport ’79. The causes of the crash were complex; this Britannica summary should suffice. It was a 1,000-year concatenation of events; the 12 Concordes still in service at the time of the crash had flown 253,000 miles in 25 years, without a single crash.
In just over a year, the BA Concorde was authorized to resume service; but in another weird coincidence, the date of the plane’s final tune-up flight was Sept. 11, 2001. After a couple months of preparation for the new security environment, Concorde service was resumed Nov. 7, 2001. But the rebirth was a brief respite from extinction.
Upon its return, every minor mishap was amplified in the press. Costs had soared, reducing loads to 50 percent capacity. Interactive entertainment made subsonic flight less boring for many flyers. And when service resumed after 9/11, passengers could no longer visit the cockpit in flight.
On Oct. 24, 2003, the last Concorde flight ended its unrivaled reign as Queen of the Skies. Air France, which had terminated service May 31, left BA in a bind, in that support costs would no longer be shared per the original 1962 agreement between the British and French governments. Airbus, successor in interest, agreed to pick up France’s share for six months. But BA could not find a buyer. It is a final irony that the airplane officially named Concorde — representing a concord between the parties — was to meet its demise when the foundational concord collapsed.
Its precipitous retirement meant that Concorde could not fly on Dec. 17, 2003, the centennial of the first powered flight. Wilbur and Orville Wright had traveled all of 120 feet — 60 percent the length of Concorde’s fuselage — in 12 seconds, during which time the Concorde at Mach 2 cruising speed covered 4.5 miles.
There are about 10 supersonic business jets (SSBJs) in various stages of development, but no prototype has yet flown. The concepts run from low-Mach 1 to Mach 3 numbers, with many aiming for higher Mach 1 numbers. All designs promise less environmental impact and a drastically lowered sonic boom. A few larger designs might produce a commercial version as well as a civilian SSBJ. For now, these all are, like the fabled Maltese Falcon of Hollywood fame said, “the stuff that dreams are made of.”
Boeing has a Mach 5 hypersonic design, which is the practical ceiling for titanium alloy airframes. Mach 6 airframes thus would require composite ceramic materials to withstand the resulting heat, and they would offer little added flight time saved over Mach 5. This appears to be decades distant.
CBS 60 Minutes aired a July 10, 2022, segment, titled “Supersonic,” on the possible return of non-military supersonic travel. It concluded that 2035 was the earliest plausible date for a new supersonic era — if all the obstacles needed to be overcome were surmounted. The program’s focus was on two key concepts: entrepreneur Blake Scholl’s company, Boom, which aims to raise $7 billion in all-private-funding—a first for supersonic planes, and the NASA-Lockheed Martin X-59 program. Scholl’s company aims to test-fly a single-seater craft this year; if successful, he’ll raise funds for a full-size plane, dubbed “Overture,” which would carry 65 passengers and serve 600 destinations around the globe. Routes would be minimum 4-to-5-hour flights and use 100 percent sustainable aviation fuel, a currently highly scarce commodity. Scholl’s long-term goal is — NOT a misprint — to enable air travel anywhere in the world in 4 hours at $100 per customer.
The NASA-Lockheed program’s primary goal is to reduce the sonic boom to a sonic thump, either little noticed at group level or barely heard. The Federal Aviation Administration (FAA) had conducted six months of sonic boom tests over Oklahoma City in 1964, using supersonic military jets. The resulting booms caused ceilings and tiles to buckle, occupant nerves to fray, and, overall, generated a massive public outcry that led to the FAA — and countries around the globe — to ban supersonic flights over land. The X-59 is slated to make its first test later this year. Eyeballing the X-59’s pencil shape, it is hard to see more than Concorde’s twin paired seats with one aisle, limiting passenger capacity.
I flew on the Concorde three times, once on British Airways, New York to London (1997), and twice on Air France, New York to Paris (1988) and Paris to New York (1997). Counting reduced time on the ground, it halved my typical regular jet door-to-door time, from 13 to 6.5 hours. Post 9/11/2001, those numbers would of course have changed. And I almost got to fly on the TU-144; in 2006, I booked a charter flight from Moscow to Almaty to watch a cosmonaut launch at the Baikonur Cosmodrome. Alas, the Russians canceled the launch. (This was seven years after the last TU-144 flight, a NASA — yes, NASA — research flight.)
Supersonic flight was a huge thrill for those lucky enough to have experienced it. The final total for 27 years of commercial supersonic flight was 2.5 million passengers. The dismal state of flight today augurs ill for a rapid return. Perhaps a supersonic business jet will be a steppingstone to a new Golden Age of Flight.
A closing bonus: Here is the only photo known to have been taken of the Concorde in actual supersonic flight.
John Wohlstetter is author of Sleepwalking With the Bomb (Discovery Institute Press, 2d. ed. 2014).