Last week, Boom Supersonic completed its first supersonic test flight of the XB-1 test aircraft. I watched the broadcast live, and the vibe was infectious, watching the hosts’ anticipation during takeoff and acceleration, and then their celebration once it was clear the aircraft had broken the sound barrier.
And yet, knowing what I know about the climate, the promise of a return to supersonic flight is a little tarnished. We’re in a spot with climate change where we need to drastically cut emissions, and supersonic flight would likely take us in the wrong direction. The whole thing has me wondering how fast is fast enough.
The aviation industry is responsible for about 4% of global warming to date. And right now only about 10% of the global population flies on an airplane in any given year. As incomes rise and flight becomes more accessible to more people, we can expect air travel to pick up, and the associated greenhouse gas emissions to rise with it.
If business continues as usual, emissions from aviation could double by 2050, according to a 2019 report from the International Civil Aviation Organization.
Supersonic flight could very well contribute to this trend, because flying faster requires a whole lot more energy—and consequently, fuel. Depending on the estimate, on a per-passenger basis, a supersonic plane will use somewhere between two and nine times as much fuel as a commercial jet today. (The most optimistic of those numbers comes from Boom, and it compares the company’s own planes to first-class cabins.)
In addition to the greenhouse gas emissions from increased fuel use, additional potential climate effects may be caused by pollutants like nitrogen oxides, sulfur, and black carbon being released at the higher altitudes common in supersonic flight. For more details, check out my latest story.
Boom points to sustainable aviation fuels (SAFs) as the solution to this problem. After all, these alternative fuels could potentially cut out all the greenhouse gases associated with burning jet fuel.
The problem is, the market for SAFs is practically embryonic. They made up less than 1% of the jet fuel supply in 2024, and they’re still several times more expensive than fossil fuels. And currently available SAFs tend to cut emissions between 50% and 70%—still a long way from net-zero.
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