Dawn of a new supersonic era

The supersonic corridor over California’s Mojave Desert is considered sacred airspace for flights that break the sound barrier. A small sensation occurred here on January 28, 2025: with a special permit from the FAA, a supersonic flight took place over land—something that is generally banned. On the day in question, the Boom XB-1 single-seater test aircraft managed to break the sound barrier several times, reaching a top speed of Mach 1.18.

These flights were intended to provide data and validate the design of the 80-seater Overture passenger jet, which the U.S. company Boom Supersonic wants to fly for the first time in 2029, ushering in a new supersonic era in the 2030s. The XB-1’s test flights were also intended to prove that the physical principle known as Mach cutoff is more than just a theory. If a supersonic flight adheres to various parameters precisely, Mach cutoff ought to prevent an audible sonic boom from reaching the ground. This proved to be the case—and could make supersonic flights over land possible in the future. That means Boom has already reached milestones that haven’t been seen in commercial supersonic flight for many decades.

Even the name XB-1 is reminiscent of history’s first confirmed supersonic flight. This was achieved on October 14, 1947, by the then 24-year-old American Air Force pilot Charles Elwood “Chuck” Yeager. German pilots had probably already broken the sound barrier several times in April 1945 with the Messerschmitt Me-262, the world’s first production jet aircraft. Yeager was in a Bell X-1, -a single-seat rocket-powered plane specifically designed to break the sound barrier for the first time in level flight, not in a dive as had been done before.

Measuring less than ten meters long, the aircraft was painted a striking orange to be more visible in the air or, in the worst-case scenario, on the ground after an accident. It was simple in design and didn’t even have an ejection seat—unthinkable in military testing today. The X-1 was mounted under the fuselage of a Boeing B-29, which carried it to an altitude of around 6,000 meters from the Muroc test site in California’s Mojave Desert. This site was renamed Edwards Air Force Base in 1950. Up in the air, the test pilot clambered into the rocket plane through the empty bomb bay of the B-29. After the X-1 disengaged, it flew on at a safe distance. Then Yeager ignited the four-chamber rocket motor, which was based on German rocket technology.

The X-1 quickly climbed to an altitude of 12,800 meters. Its fuselage was patterned after a standard bullet—a projectile that had proven to be particularly stable at supersonic speeds. But this shape is rather ill-suited to the aerodynamics of ordinary aircraft. At cruising altitude, Yeager accelerated the aircraft to Mach 1.06, which is equivalent to 1,079 kilometers per hour. Observers on the ground heard a dull double bang—a sound that would recur from then on whenever the sound barrier was broken over Edwards: the sonic boom that is still unavoidable today. Just 14 minutes after disengaging and making his historic flight, Yeager landed the X-1—without power, but with success—back at Muroc.

A victory for the Soviet Union: The Tupolev Tu-144

In its earliest decades, supersonic flight was exclusively military in nature. But as the 1960s drew to a close, the race was on between East and West to see who would get the first supersonic passenger plane into the air. This accolade went to the Soviet Union when, on December 31, 1968, the Tupolev Tu-144 took off on its maiden flight. It was a world sensation: the elegant aircraft with white delta wings could carry as many as 140 passengers and reach speeds of up to Mach 1.88. While its counterpart in the West, the Franco-British Concorde, wouldn’t take off until March 2, 1969, it could fly at Mach 2.02—twice the speed of sound. At that time, the aviation industry assumed that all longer passenger flights would soon be carried out by supersonic jets. The Boeing 747, which was developed in parallel, was intended more for cargo. A future full of supersonic dreams seemed within reach.

But things turned out differently: the 1973 oil crisis made kerosene extremely expensive, and concerns grew about engine noise and sonic booms. The Tupolev Tu-144 performed only pro forma “regular” flights through the end of 1978. Although the Concorde was an economic failure, between 1976 and 2003 it proved to be a popular means of transportation for business executives and celebrities in a hurry. This was especially true on the busy routes from Paris or London to New York, which it could complete in just about three hours. But with round-trip ticket prices of around 7,000 euros in today’s currency, this remained a pleasure for an exclusive group.

60 years after the Concorde’s maiden flight—a new supersonic era?

Some 20 years after the Concorde was retired, Boom Supersonic is now venturing into the next supersonic era with the Overture. Debuting 60 years after the Concorde’s maiden flight, it is expected to carry between 65 and 80 passengers and reach Mach 1.7 over water. For flights over land, Boom plans to stay just below the sound barrier at Mach 0.94.

If the overland ban were to be lifted, the Overture could achieve speeds of up to Mach 1.3 in “Boomless Cruise” with no noise pollution on the ground. In its X-59 QueSST project (see interview "Research on how to achieve a quieter sonic boom"), NASA is also currently researching shapes for supersonic aircraft designs that should reduce the boom enough to permit overland flights. Three major carriers—Japan Airlines, United Airlines, and American Airlines—have preordered a total of 132 Overture jets.

Supersonic flight in the 2030s is expected to have far less impact on the environment than the Concorde did. For example, the Overture engineers are aiming to reduce the noise of both the takeoff and the sonic boom—each of these is to be lower than the Concorde’s values by a factor of 30. At the same time, the plan is for the engines to run exclusively on Sustainable Aviation Fuels (SAFs). The whole thing is calculated such that a ticket should cost no more than a trip today on the same route in business class. After 75 years, the stage is set for a new era of supersonic travel.