In June 2021, United Airlines announced plans to start offering supersonic passenger flights by 2029. The US airline has agreed to purchase 15 new supersonic aircraft as part of its efforts to “return supersonic speeds to aviation.”
The last supersonic flight touched down in 2003, when the Concorde was retired by British Airways and Air France. The United deal is conditional upon the new airliners meeting safety standards—the aircraft, named Overture, is yet to be flight-tested. Overture’s Denver-based manufacturer, Boom Supersonic, reports that they designed the net-zero carbon aircraft to fly on 100% sustainable aviation fuel.
What is supersonic flight?
Supersonic flight occurs when an aircraft accelerates past the speed of sound, breaking the sound barrier. While a typical passenger jet cruises at around 560 mph at an altitude of around 40,000 feet, supersonic flight demands a minimum speed of 660 mph at about 60,000 feet.
Overture is expected to almost double that benchmark, reaching speeds in excess of 1,120 mph and cutting in half transatlantic journey times such as flights from New York to London. Boom claims their Overture aircraft could complete that journey in just 3.5 hours. The Concorde, which first started flying commercial passengers in 1976, was actually faster, reaching maximum speeds of around 1,350 mph.
Supersonic flight sparks two major concerns: pollution and noise. As Boom’s Chief Commercial Officer Kathy Savitt explained to the press, to fly supersonic, you need more power, which requires more fuel. Nevertheless, she maintains that Overture will operate as a net-zero aircraft in terms of carbon emissions.
Another potential concern with the new United fleet is noise on the ground. When an aircraft breaks the sound barrier it creates a sonic boom, which on the ground may be mistaken for an explosion or clap of thunder—hence the manufacturer’s name. Civil aviation laws dictate that aircraft cannot break the sound barrier above populated areas since the bang is incredibly loud and would disturb residents. Typically, a supersonic aircraft must wait until they are out over the ocean to break the sound barrier.
Boom maintains that Overture will be no louder than a regular passenger jet during takeoff, flight, and landing. A spokesperson for the company said that significant improvements in aircraft design since the days of the Concorde would help reduce and mitigate the sonic boom.
How can supersonic travel be sustainable?
Overture will be powered by sustainable aviation fuel (SAF), according to Boom. This could take the form of biodiesel derived from everything from agricultural waste products to purpose-grown high-energy crops. However, the world still has nowhere near the capacity needed to produce enough biofuel for the entire aviation industry.
Nevertheless, Boom maintains that power-to-liquid processes, where renewable energy is used to make liquid fuel, could close the gap. As a Boom representative explained, the company expects that with billions of airline commitments and investments across the sector, biofuel production will be ramped up well before 2029.
What happened to the Concorde?
The Concorde was one of only two working commercial supersonic jets to date. Operated by British Airways and Air France, 20 Concorde aircraft were built in total, of which 16 flew.
Launched in 1976, the aircraft was in service for 27 years before being decommissioned in 2003 following a farewell tour around the UK and North America. Capable of carrying around 100 passengers and a crew of nine, the Concorde once travelled from London to New York in just 2 hours, 52 minutes, establishing a new record.
Due to the sonic boom, the Concorde was banned from flying over land. Because of this, it primarily served the transatlantic route between London or Paris and Washington, DC, or New York. Because of the significant time savings achieved by the Concorde, combined with its elite status, operators charged as much as $12,000 (in today’s dollars) for a round trip. This meant that the aircraft only had to fly at half capacity in order to break even.
In 2000, the plane was grounded, after an Air France accident killed all 109 passengers and crew onboard, as well as four people on the ground. It was the only fatal accident of the Concorde in its history. Significant modifications were mandated for the remaining fleet, with the first Concorde flight to take passengers since the accident landing in New York on September 11, 2001, minutes before the first plane hit the World Trade Center. In the wake of 9/11, the bottom fell out of the premium airline industry, leaving British Airways and Air France unable to recoup their modification costs.
Despite the astronomical development costs, the Concorde did become profitable in its last years of operation. Although some experts maintain that the world’s wealthiest travelers will stick with their private jets rather than travel with other people, Boom argues that its research suggests otherwise. Company founder and CEO Blake Scholl explained that being able to travel twice as fast will allow passengers to experience the benefits of “life lived in person,” like longer, more relaxing vacations to far-off destinations, and more productive business relationships.