In October 2003, British Airways flew Concorde from New York’s JFK to London Heathrow at a top speed of 1,354mph for its last voyage. The market for a plane that could travel at twice the speed of sound had disappeared.

Sixteen years later, a race is on to bring it back.

Several aerospace companies are working on a revival of supersonic commercial passenger planes that can fly at more than 660 miles an hour at above 30,000 feet. The start-ups are looking at planes that could fly at 1,000mph, 1,500mph, and even 3,500mph, or Mach 5, five times the speed of sound.

At such a speed, the trip from London to New York would take a little over 90 minutes, leaving passengers barely enough time to watch a full film. The typical journey time at present is seven hours.

The projects have been met with scepticism from experts who believe tickets will be too expensive to make flights viable, however. Concorde burnt twice as much fuel as a Boeing 747 and carried a quarter of the number of passengers and its prices meant that it was mostly restricted to rock stars, actors and chief executives. Most of the supersonic jets being designed today will carry even fewer passengers, ranging between 12 and 70 people.

That has not stopped such companies amassing funding from investors keen not to miss out on a potential revolution in long-haul travel. Some of the groups are also working in partnership with established plane makers such as Boeing and Lockheed Martin.

Most of the supersonic jets
being designed today will carry between 12 and 70 people.

In Atlanta, a one-year-old start-up called Hermeus has just received undisclosed funding from the American venture firm Khosla Ventures to create a plane that can travel at between 3,500 and 3,800mph.

The company is made up of aerospace engineers who met working on a hypersonic rocket plane for the US air force. They had all been part of the Amazon founder Jeff Bezos’s Blue Origin space exploration venture or Elon Musk’s space rocket firm SpaceX. The speeds on Hermeus planes would be so fast that passengers would probably be pushed back into their seat for the first 15 minutes of a journey that would reach a much greater altitude than a conventional plane, about 90,000ft.

At such a height, the air is thinner so there is less resistance in the atmosphere. The sheer speed of the plane also means that the dynamic pressure on the aircraft would be so intense that flying at 30,000ft would probably cause the plane to disintegrate. AJ Piplica, co-founder of Hermeus, expects the plane to be commercially ready within a decade. He said: “We want to do something that will change the way the world works and this is it.”

Over in Denver, a five-year-old start-up called Boom is creating a commercial passenger plane called Overture that will travel at speeds of Mach 2.2, or roughly 1,451mph and would seat 55 to 75 people. The company believes it will enter service by the mid 2020s.

Viability Uncertain

Boom has said it will need to raise $6 billion to get the plane to market but has announced orders for 30 planes from Japan Airlines and Virgin Group.

Experts are not sure about its viability. Bob van der Linden, of the Smithsonian Institution, said the cost of fuel needed to travel at such speeds means cabin sizes would remain small. The jets are likely to burn three to four times as much fuel per business-class passenger as standard planes.

“Concorde failed because it was not an economically viable business model, the tickets were too expensive,” Mr Van der Linden said. “There have been no technological breakthroughs since then that will enable an airplane to go supersonically for the same amount or less money than a subsonic airliner.”

Such flights emit a loud continuous “sonic boom”, which can even jolt buildings, and most countries have banned supersonic jets from flying at such speeds over land, wiping out many of the world’s viable airline routes.

However, Nasa has started work on a supersonic aircraft called the X-Plane that may have a mild enough boom for citizens to bear flights over cities and towns, which they will test in 2021.