And if global expectations hold true, elsewhere, air travel will just go up and up. In its recently released 2023 commercial market outlook, Boeing Co. predicts the world’s fleet of commercial planes (now numbering just over 24,500) will double by 2042. More planes, more passengers and the continuing predominance of larger aircraft add up to a big climate takeaway: Sustainable aviation fuel will be critical to the effort of decarbonizing the industry. 

Today, two-thirds of the world’s planes in commercial operation are single-aisle models such as the Boeing 737 and the Airbus a320. Small regional jets and freight airplanes each make up 9% of the total. Only 15% of the global fleet is made up of wide-body models such as the Boeing 787 and the Airbus a350. 

The global fleet of the future will skew single-aisle even more than it does now. Wide-body planes are also expected to increase substantially in number and the freighter fleet will grow. Meanwhile, regional jets’ share will shrink slightly, to less than 5% of the total. 

There are climate implications in all of this, starting with the obvious fact that doubling the world’s planes in service and greatly increasing passenger travel will increase fuel consumption. Data from the International Energy Agency shows that over the past two decades, the energy intensity of commercial aviation has decreased by almost 50% for domestic trips and by about 40% for international trips. Even so, the volume of air traffic rose so much over the same period that it led to a doubling of direct emissions from aviation. 

Importantly, the distribution of those emissions tilts strongly toward the longest flights. Commuter, regional and short-haul (up to 2-hour) flights, on planes with between nine and 150 seats, together are responsible for about 27% of total aviation emissions. Medium- and long-haul flights make up the other 73%. 

Approaches to reducing aviation emissions include electrification and hydrogen fuel cells and combustion. Electric air taxis may be able to power some of the commuter market by 2025, and hydrogen could fuel short-haul flights by mid-century. 

But removing the emissions from every last mile of today’s commuter, regional and short-haul flights would only shrink aviation’s current climate footprint by about one-quarter. The one technology capable of meeting the needs of every commercial aviation use case is sustainable aviation fuel. It is also the only source available to address the remaining 70-plus percent of today’s emissions from the sector. 

Sustainable aviation fuel is much more expensive than conventional jet fuel and currently accounts for only 0.1% of jet fuel use, according to BloombergNEF. Even if scaled-up production helps narrow the gap, steep costs look hard to avoid. 

With the global fleet about to grow substantially and passenger traffic continuing to rise, today’s airborne decarbonisation challenge is expanding. The challenge is to address every part of the market wherever possible, and at the same time, focus on a critical and probably unavoidable fact: Sustainable aviation fuel must be adopted at scale to lessen the climate impact of the biggest jets and the longest flights. 

Nat Bullard is a senior contributor to BloombergNEF and writes the Sparklines column for Bloomberg Green. He advises early-stage climate technology companies and climate investors. DM