Why one trip can matter so much
Flying is unusual because it makes very long journeys quick and easy. The emissions from an aircraft are not especially high per mile compared with some other transport, but the distances are so large that a single return flight can add up to a considerable amount of carbon dioxide. For a person who otherwise uses little energy, one long-haul holiday can be a notable part of their yearly footprint. For someone who flies often, aviation can dominate it.
The exact size depends on the flight, the aircraft, how full it is and the method used to calculate it. Online tools give different answers, so treat any single figure as an estimate. Footprint calculators are useful for comparing options, but they can differ in what they include and the assumptions they use.
What makes aviation emissions hard to cut
Several features explain why flying is difficult to make cleaner:
- Energy needs. Lifting a heavy aircraft and its fuel into the air takes a lot of energy, and fuel must be carried for the whole trip. Fuel is burned most heavily during take-off and climb.
- Fuel. Jet fuel is energy dense, which batteries cannot yet match in weight for long routes. Electric or hydrogen aircraft are being researched but are generally not expected to replace conventional long-haul flights soon.
- Alternative fuels. Sustainable aviation fuels, made from waste oils, residues or other sources, can reduce life-cycle emissions in some cases, but supply is limited, they are more expensive, and the benefit depends on how they are made. They are generally blended with conventional fuel.
- Long lifetimes. Aircraft last for decades, so changes to fleets come slowly, although newer aircraft are typically more efficient than older ones.
- Non-CO2 effects. Flying at altitude also produces contrails and other effects that influence the climate. Scientists agree these matter, but their size is less certain than that of carbon dioxide, so published estimates differ. This is one reason why a simple figure for a flight can understate or overstate the full picture.
Aircraft efficiency has improved over the years, but growth in the number of flights has tended to offset some of those gains.
Cost and fairness
Flights can be cheap relative to their environmental cost, and fuel is taxed differently from other fuels in many places. Not everyone flies, and a small share of people often accounts for a large share of flights. These are policy questions beyond what an individual can change, but they help explain why some travellers feel their choices are limited and why collective action matters here.
The real options for travellers
You cannot remove every flight from your life, and you may not want to. The useful question is which choices make a meaningful difference. In rough order, they are:
1. Fly less often or not at all. Skipping a flight is the most direct way to avoid its emissions. Some people set themselves a limit on flights per year, or swap a short break abroad for a closer destination.
2. Choose a shorter distance. A destination reachable by a shorter flight, or none, generally has a lower footprint. Fewer, longer stays rather than many short trips also spread the impact over more days.
3. Switch to the train or coach where practical. On routes where it is realistic, overland travel usually has a lower footprint per passenger and can be a more relaxed experience, although it takes longer and may cost more. Check the journey time, cost and connections before you decide.
4. Choose the flight carefully. If you have to fly, some choices can help at the margin:
- Direct flights avoid the extra take-off and climb of a stopover, though a slightly longer routing is not always worse.
- Economy seats typically account for a smaller share of an aircraft’s emissions per person than business or first class, because they take up less space.
- Travelling light reduces weight, although the effect of a single bag is small.
- Newer, more efficient aircraft and airlines with full planes can be better, but information is not always available and claims should be checked.
5. Consider whether the trip is needed. Video meetings can replace some business flights, and some reasons for travel, such as visiting family or an important event, are not negotiable. These are personal decisions.
6. Think about offsets or fuel schemes carefully. Some airlines and booking sites offer to offset a flight or to fund sustainable aviation fuel. These schemes vary in quality, and they should be seen as a supplement rather than a substitute for flying less. Useful questions include what the money funds, whether it is independently verified and how permanent the benefit is.
Making a plan that you can keep
Many people find it easier to be specific than general. You might decide to take one long trip every few years and spend the rest of your holidays closer to home, or to take the train to places within a certain distance. A rule you can follow is more useful than a perfect one you drop.
It also helps to keep other parts of your travel in proportion. Reducing a car habit is worthwhile, but it will not usually cancel out frequent flying. Equally, flying occasionally does not make other choices pointless.
Avoiding both guilt and complacency
Flying connects families and communities, supports economies and makes experiences possible that many people value. The footprint is real, but personal guilt is not the only useful response. It is reasonable to make a change you can sustain, to support better rail and cleaner fuels, and to accept that you will not get everything right. What is best depends on your circumstances, and the effect of any one decision is uncertain.