Prioritising all-economy cabins, maximum passenger loads, and using only the most fuel-efficient aircraft could slash global aviation emissions by up to 75%, according to new academic study led by the University of Oxford.
The research, published in the journal Communications Earth & Environment, suggests that the aviation industry’s primary decarbonisation tools, such as the UN’s CORSIA offsetting scheme and the EU’s ReFuelEU mandate for Sustainable Aviation Fuels (SAF), are woefully unambitious when compared to the immediate gains to be had from increasing efficiency.
In fact, the authors say that these policies could even be making the situation worse. “Paradoxically, this legislation could lead to an increase in overall warming, even if quotas are successfully met, if total fuel use increases faster than the share replaced with SAF,” they say.
The report raises the question of whether low-fare operators, often criticised for driving volume, may actually be environmental leaders.
Airlines such as Ryanair and Wizz Air have long operated the very model the Oxford study advocates: high-density, all-economy cabins and industry-leading load factors.
Current mandates like ReFuelEU focus on a slow, decades-long transition to alternative fuels. However, the researchers argue that the “avoidance potential” of efficiency measures is so vast that continuing to fly half-empty planes with luxury seating is becoming climate-indefensible.
While legacy carriers often boast about their investment in SAF, their reliance on heavy, space-consuming business class seats and lower passenger densities per flight-km results in a significantly higher carbon footprint per passenger.
“Our results show that efficiency-focused policy could swiftly reduce aviation emissions by more than half, without waiting for future fuels,” said co-author Dr Milan Klöwer. “These are tools that we can use right now.”
By analysing 27 million commercial flights from 2023, researchers found that the industry is effectively “leaving carbon on the table.” While SAF remains expensive and scarce, and offsetting is increasingly dismissed as a greenwashing exercise, the study identifies an 11% reduction in global emissions that is achievable today—simply by using the most efficient aircraft already in existing fleets on the routes they currently serve.
To reach the 75% reduction target, the authors say a “maximalist” efficiency scenario is called for, entailing a transition to all-economy seating layouts and ensuring every flight is filled to capacity.
With aviation policy currently fixated on technological “moonshots” like hydrogen and electric flight, the paper suggests that the most effective climate solution may not be a new fuel, but a more disciplined way of flying.
“While economically and practically unfeasible to replace all older aircraft short term, this analysis shows the potential more efficient aircraft have in comparison to other efficiency gains,” said Dr Klöwer.
“Realistically, this would be a long-term transition – one that could be promoted by policies that reward efficiency, so that the most efficient aircraft are favoured whenever replacement decisions are made.’
The authors suggest that a combination of “soft policies” such as a public airline efficiency rating, combined with market-based measures such as cutting subsidies and higher landing fees for inefficient airlines or aircraft and regulation on CO2 intensity gaps may be needed to increase operators’ use or more efficient practices.
They point out however that such an approach is likely to be met with resistance from within the industry.
“Resistance to any such policies must be expected, as airlines operate within economic constraints, a business environment shaped by subsidies, expectations of continued growth, and limited ambition for climate change mitigation,” they conclude.
Image: Rob Munro
The new study suggests the low-fare model may be the most environmentally-friendly.
