When you learn that a Boeing 747-400 jumbo jet burns through four litres of fuel a second, it becomes abundantly clear why flying is such an energy-intensive and climatically destructive activity. In fact, just one flight can produce as much CO2 as many people do in a year.

Although aviation is a relatively modest greenhouse gas (GHG) emitter compared with other sectors (accounting for around 2.5% of global CO2 emissions), it is one of the fastest growing. Globally, the number of flights a year is forecast to skyrocket in coming decades, having already grown 5% a year since 2000.

The aviation sector accounts for around 2.5% of global CO2 emissions. (Photo by Ian Schofield via Shutterstock)

Internationally, the UK’s aviation industry is one of the worst offenders: despite the country’s diminutive size, it is the third-largest aviation emitter behind the US and China. “Heathrow is one of the busiest airports in the world; and incredibly, one in 12 flights globally are undertaken on a British passport,” says Matt Finch, UK policy manager for Brussels-based NGO Transport & Environment (T&E). “As a nation, we really love flying.”

The UK government is set to publish its Jet Zero strategy for decarbonising the sector in July 2022. Up until now, the industry has set its own goals for cutting its environmental footprint. However, a couple of high-profile reports published in recent weeks have highlighted a distinct lack of progress made towards those targets and begged the question: does the government need to step in and limit the Brits’ penchant for flying?

Missed climate targets

Air travel accounts for approximately 7% of the UK’s GHG emissions. In 2019, the last 'normal' year before the pandemic, the sector emitted 38 million tonnes of carbon – around the same amount as all the trucks on the road and just over half of all the cars. However, the sector’s emissions are growing at a worrying pace. “When you look at most other sectors of the economy, their emissions are either flat or falling quite rapidly,” says Finch. “Aviation is the exact opposite, the curve is nowhere near flat, it is steep and rising, and that is simply because, while the planes have been getting more efficient, demand for flying has outstripped everything.”

Over the past decade, the sector has heavily emphasised two approaches to decarbonisation: zero-emission aircraft and sustainable aviation fuel (SAF). Both have been progressing technologically and have received increasing levels of investment: there are now commercial plants producing SAFs, there are a handful of zero-emissions aircraft companies, and there have been test flights over the UK using electric and hydrogen fuel cell planes. The problem is the progress is just not happening fast enough for the sector to get anywhere near net zero by 2050.

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“There has been a general feeling in recent years that the sector isn’t doing enough by itself,” says Finch. “This is why we need government regulation. There are absolutely no repercussions for the airlines not hitting their climate targets.”

New research published by the climate charity Possible earlier this month revealed that UK airlines have missed all the climate targets they have set themselves since 2000, except for one. Most of the goals focused on using greener fuels to power planes or making fuel more efficient. easyJet was the only airline to accomplish a solitary target, reducing fuel burn per passenger kilometre by 3% by 2015.

There is some regulation on the horizon. The UK and the EU are set to introduce ‘SAF mandates’, where fuel suppliers will be obliged to sell a minimum – and increasing – percentage of SAF in their total fuel mix. “The knock-on effects of that means fuel suppliers have to invest in SAF plants, they have to work out where they will get their supplies from, they have to sort the supply chain out, etc.,” says Finch. “And the very fact that the UK and the EU are going to put this in place has meant the whole SAF industry is having a massive boost right now.”

Are demand reduction policies necessary?

Having published consultations on its proposed approach in July 2021 and March 2022, the UK’s Jet Zero strategy looks set to go against guidance from advisers in the UK Climate Change Committee – which has petitioned for deliberate policies to manage growth in demand for air travel – and instead rely on the aviation sector to reduce its own emissions while growing the number of flights provided.

However, another report published in recent weeks by energy consultancy Element Energy (EE), commissioned by the Aviation Environment Federation (AEF), a UK-based non-profit, concluded that demand reduction is required for the country to hit its economy-wide climate targets. The Jet Zero plans overestimate the likely improvements in operations, technology and alternative fuels and rely on uncertain solutions, found the research.

The report highlighted significant risks in the strategy, including relying on improved system efficiencies, assuming high SAF uptake, a misleading portrayal of SAF emissions abatements and failing to account for the non-CO2 impacts of aviation (the nitrous oxide, sulfates and contrails emitted by planes cause more warming than the carbon they emit). While new technologies and fuels will be necessary, they are unlikely to be developed at the speed and scale needed to deliver net-zero aviation by 2050 without parallel reductions in demand, stated the authors.

The report concluded that a halt to airport capacity growth and demand reduction measures pose a far less risky approach to hitting net-zero aviation and the 78% economy-wide emissions cut to which the UK government has committed by 2035. EE argues for an alternative approach that requires the sector to make deeper cuts to its emissions in the near term to help reduce risk and to minimise the total amount of CO2 emitted between now and 2050.

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Those demand reduction measures could include reducing passenger demand through carbon pricing, an air miles or frequent flyer levy, fuel duty, VAT or reforms to Air Passenger Duty (an excise duty charged on the carriage of passengers flying from a UK airport).

“The government’s plan is to sit back and allow both airports and emissions to grow in the short term while hoping for future technologies and fuels to save the day,” says Cait Hewitt, policy director at the AEF. “[There is a] need for action now, including ruling out airport expansion and limiting demand.”

Non-profit the International Council on Clean Transportation (ICCT) agrees that the UK will need to consider options to constrain air traffic growth to reduce in-sector emissions in line with the Paris Agreement. “It depends on how fast other sectors decarbonise, but under a 1.5°C future, UK aviation would more than double its share of aviation’s proportional carbon budget under Jet Zero without demand management,” says Dan Rutherford, the ICCT’s programme director for marine and aviation. “So we expect policies like not expanding airports, carbon pricing and/or a frequent flyer levy will be needed.”

Charity Possible is lobbying for a frequent flyer levy, the idea of progressively taxing frequent flying and thereby constraining demand for flights. This would see everyone get one tax-free return flight each year but add a gradually rising tax on any subsequent flights, a policy that proved popular at the UK's citizen climate assembly last year. The charity argues a frequent flyer levy is a fair alternative to manage demand by placing a higher tax on individuals who fly more often, such as the 15% of flyers who Possible estimates take 70% of all UK flights.

“By focusing demand reduction policy on the small minority of people who are responsible for almost all of the environmental damage from air travel, it will be possible to maintain access to some air travel for everyone, at the same time as keeping overall levels of flying within safe limits for the climate,” says Leo Murray, Possible’s director of innovation.

Net-zero aviation

The industry, however, sees things differently. “Flying is not the enemy, carbon is,” says a spokesperson for airline trade body the International Air Transport Association (IATA). “If aviation is sustainable then there should be no barriers to people’s desire to fly and explore the world.” In IATA’s estimations, SAFs could represent up to 65% of the abatement needed to reach net zero, with production capacity under construction today likely to exponentially increase the supply of SAFs by 2030.

“Instead of the outdated and ineffective approach to tax people out of the skies, governments are rightly looking towards technological solutions that will enable the world to stay connected while doing so in a sustainable way,” says the spokesperson. “The UK Jet Zero initiative is an important example of this, and we support its aims.”

The organisation suggests governments should agree a sector-wide long-term climate goal for air transport at the UN International Civil Aviation Organization’s triannual assembly later this year.

Finch, for his part, stands somewhere in the middle of the two opposing positions. He agrees that demand needs to be reduced but thinks there are subtler approaches to direct restrictions such as the frequent flyer levy. First, similar to the SAF mandate, the government could introduce a ‘miles-flown mandate’ for zero-emission aircraft, which would compel investment in the industry. Second, the government could introduce a kerosene tax akin to the fuel duties on cars. That would increase the costs on the industry and push up the prices of flights, thereby reducing demand and encouraging further investment in SAF and zero-emission aircraft.

“When people think about demand reduction, they think they won’t be allowed to fly, but actually all it is is bringing demand back down to manageable levels," he says. "So that means in, say, ten years’ time, there may still be more flights, just not as many flights as there would have been without any measures in place. If demand keeps increasing by 5% per year, there is no way the technological solutions will ever be able to make up the ground, and certainly not by 2050.”

Indeed, T&E has cautioned against setting targets for SAFs too high because of concerns over a lack of sustainable supply. Pushing airlines to use more biofuels could lead them to switch to unsustainable food-based biofuels, such as those made from palm oil and linked to deforestation. Synthetic fuels such as e-kerosene have more potential for scale up but there is still almost no production right now. The ICCT forecasts only a small volume of synthetic fuels being used in aircraft by 2030, just 0.2% of the total 5.5% of SAFs it says could be used in the EU by 2030.

“What I would also like to see is a real focus on emissions,” adds Finch. “I would like the government to come out and state the pathway the sector should be on, and if it strays too far off that pathway, demand measures x, y and z will be imposed on them.”

Few bellwethers

Unfortunately for Boris Johnson and his administration, there are not too many successful models in the global aviation space to copy and paste, says Finch.

In 2019, 50 million litres of SAF were used in flights, just 0.01% of global aviation fuel, meaning the industry missed a goal set in 2010 to use 6% by 2020. However, 32 countries including the likes of France, Norway, the US and Sweden now have SAF policies in place. The Netherlands, for example, has said that 14% of its aviation fuel must be sustainable by 2030.

Countries such as Austria and France have also made moves to curb short-haul flights on routes where there is a rail connection. “The French have said that where there is a direct train you can do within four hours, the flight is banned, and that makes perfect sense because it is quicker on all the routes they have banned to take the train,” explains Finch.

Norway has stated that from 2040 it will only permit zero-emission aircraft for domestic routes. Because of the mountainous terrain, many of the country's flights are short in terms of distance but would take a long time to travel by train or car. “That is why there are a lot of small planes flying short distances – which is perfect for zero-emission aircraft,” says Finch. “The first zero-emission aircraft will be small and will fly relatively short distances, and as they get better, they will grow in size and flyable distance.”

Scotland has also stated its desire to only use zero-emission aircraft and it is a policy Finch believes could be rolled out across the UK. “We are a small country: 5% of the domestic flights are between Glasgow/Edinburgh and London, for which there are 40 odd trains a day,” he says. “So, we could comfortably reduce the size of our domestic market whilst also saying that from a future point we are only going to have zero-emission aircraft.”

Looking ahead, Finch forecasts more aviation policies coming from the government, and despite its “lack of sticks, over-reliance on technological breakthroughs and insufficient urgency”, there is some “good stuff” in Jet Zero – such as the SAF mandate.

“They are trying,” he says. “They are probably on a C-grade at the moment – but there is a long way to go for an A.”