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Commercial aviation has transformed global economies, long-distance relationships and access to the breadth of the human experience. In the 1970s, the first commercial wide-bodied jet, the Boeing 747, took to the skies and boldly defined economical air travel. Wider planes resulted in more seats per aircraft, and therefore flight tickets were made cheaper. The ultra-low cost flight carrier Ryanair has made it possible to travel internationally for as little as the cost of a coffee and sandwich. It has never been easier or cheaper to fly — but what is the true cost to the planet?
Flights produce greenhouse gases — mainly carbon dioxide — from burning fuel, which contributes to global warming. Emissions per kilometre travelled are known to be significantly worse than any other form of transport. As such, aviation is one of the most polluting industries, creating potentially one of the most wicked problems to solve in the sustainability space – how can international travel be made more sustainable, when flying is often the only way to get from one country to another? The solutions are undoubtedly multi-faceted – some include heavier taxation on certain flights, improving international rail and sail infrastructure, as well as development of more sustainable jet fuels.
It is clear that we need to reduce our flying collectively, but there is a difference in emissions depending on how you fly. The average holiday-maker, when challenged with the moral dilemma of flying less, tends to believe that the focus ought to be on private jets commandeered by celebrities and Premier League football teams alike. The latter has recently been under some media scrutiny: In March 2023, BBC Sport found evidence of 81 individual short-haul domestic flights made by Premier League teams to and from 100 matches during a two-month sample period — some of these flights were as short as 27 minutes.
Domestic flights are so much more emitting than short haul or long haul because take-off requires much more energy input than the ‘cruise’ phase of a flight. According to The International Council on Clean Transportation (ICCT), the carbon intensity (how many grams of CO2 are released to produce a kilowatt hour (kWh) of electricity) is very high on very short flight distances of less than 1,000 km. The intensity falls with distance until around 1,500 to 2,000 km; which then levels out and changes very little with increasing distance. The ICCT also notes that often less fuel-efficient planes are used for the shortest flights.
Private jets are even less energy efficient, often transporting very few passengers, and generally produce significantly more emissions per passenger than commercial flights. Dr. Debbie Hopkins, an expert in decarbonising transport at the University of Oxford, explains: “A huge amount of fuel is used during takeoff and landing of a plane, no matter how many people you have on board. So an already polluting mode of transport (commercial aviation) becomes even worse (with private jets)”. If private jets, business class and first class are off the table, is there a way to make travelling in economy more sustainable?
In February 2023, The Royal Society, a UK science academy, published a report that warned of no single, clear, sustainable alternative to jet fuel able to support flying on a scale equivalent to present day use. According to the report: “Producing sustainable aviation fuel to supply the UK’s ‘net zero’ ambitions would require enormous quantities of UK agricultural land or renewable electricity to keep flying at today’s levels”. The report explores four alternative fuels which support the decarbonisation of the sector: hydrogen, ammonia, synthetic fuels (e-fuels) and biofuels.
These fuels were assessed against:
Having scoped the existing research base, the report had several conclusions, including:
The report concluded that all alternative fuel options had advantages and disadvantages; there is no clear contender which can be considered most environmentally friendly.
Whilst there are lots of questions left to answer, we can be certain of a few things. A combination of alternative fuels will be needed to decarbonise flying, but flying at its current rate cannot be sustained by alternative fuels. The research is clear that long haul flights are less emitting than short haul flights and travelling in economy is far less emitting than business, first class and private jets. Undoubtedly, research into the best alternatives and investment to make them viable options is urgently needed. Until then, we recommend keeping your private jet in storage, flying economy when needed, considering local holidays and finding alternative transport methods.