Supersonic and sustainable? How aviation plans to break the sound barrier - and its reliance on jet fuel

A new era of supersonic flight is on the horizon with major airlines placing orders for the next generation of ultrafast jets.

American Airlines has committed to buy up to 20 Overture jets, which are being developed by Boom Supersonic. American Airlines has an option to buy a further 40 planes. United Airlines has ordered 15 aircraft and may commit to 35 more. The current pre-order book runs to 130 aircraft.

The orders for Boom’s Overture aircraft come almost 20 years after Concorde was grounded, bringing a close to the first age of supersonic passenger planes.

Overture promises to bring back transatlantic flights in a fraction of the journey time of subsonic aircraft, with a cruising speed of Mach 1.7 - almost twice the speed of today’s fastest commercial aircraft.

Boom says the plane is more than just a transatlantic workhorse, forecasting profitable operations on more than 600 routes worldwide. Overture will have a range of almost 5,000 miles (8,000 kilometres) and will carry up to 80 passengers. It will only fly supersonic over oceans, to avoid inflicting sonic booms on populations.

Questions about demand for a new generation of supersonic jets have arisen since the pandemic, with calls on Zoom and Teams replacing the need to cross oceans and continents for business meetings. Research from the World Travel and Tourism Council shows business travellers spent $1trillion on flights in 2019. It’s forecasting business travel spending will return to two-thirds of pre-pandemic levels this year. Boom will hope its aircraft can succeed where Concorde failed; attracting enough passengers to make the Overture viable for airlines to operate.

A crucial difference, says Boom, between Concorde and Overture is that the new plane will be carbon neutral, powered by sustainable aircraft fuels (SAFs) that are currently in the development phase. The infographic below shows how green aviation fuels can be made by recycling household waste and oil. These are converted into a fuel-production feedstock. After processing, this is mixed with traditional jet fuel. Air bp says using SAFs can reduce an aircraft’s lifecycle carbon emissions by 80%, compared to traditional fuels.

Another process for making clean jet fuel, known as Power-to-Liquids, uses electricity from renewable sources to power electrolyzers that create green hydrogen. This is then mixed with CO2 captured from the atmosphere. The liquid hydrocarbons from this process are converted into synthetic kerosene aviation fuel.

The major challenge for this new generation of supersonic jets will be the production of SAFs at a viable scale. Andreas Hardeman, Aerospace and Drones Lead at the World Economic Forum, says current levels of production amount to a drop in the ocean.

“Today, SAF represents less than 0.1% of all jet fuel, so that’s nowhere near where we need to be. In addition to scaling up production capacity, we’ll need regulatory and fiscal policies to help reduce the cost differential between the SAF fuels and conventional jet fuel.”

The World Economic Forum has launched the Clean Skies for Tomorrow Coalition, a public-private collaboration that’s helping the aviation sector move towards net-zero emissions. Accelerating the scale of SAF production is a central pillar of the coalition’s work. It has developed aviation fuel policy toolkits to help governments as they embark on clean aviation strategies.

Andreas Hardeman also believes organizations like the American Society for Testing Materials (ASTM) will be central in dictating the pace of the transition to clean jet fuels. “Ultimately, once the international certification bodies will allow the use of 100% SAF, we expect to see significantly increased momentum to scale up production and an acceleration in aviation emissions cuts.”