One Percent of People, Half of Flying’s Emissions

Most people do not fly at all

The headline result is about concentration. According to Lund University’s summary of the paper, only about 11 percent of the world’s population used air transport in 2018, and slightly less than 4 percent took an international flight. Flying, in other words, is something a minority of humanity does in any given year.

That minority is not evenly spread. In industrialised countries, the researchers found that almost half of inhabitants use air transport in a year, while in much of the world the share is far lower. Gössling has stressed that even in wealthy countries, it is still fewer than half of people who fly annually — so “everyone flies now” is not true even where it feels true.

The sharpest figure concerns frequent fliers. The most frequent flyers make up about 1 percent of the world’s population, yet they account for more than half of the carbon dioxide emitted by passenger air travel. At the far end, the university’s summary notes that individual private aircraft users can be responsible for up to 7,500 tonnes of CO₂ a year.

Why this matters for a personal footprint

Global averages blur this picture. Spread across everyone on Earth, aviation looks like a modest slice of emissions. Concentrated in the people who actually fly, it can become the largest single item in a year. That is why two people in the same city can have very different footprints for reasons that never show up in their daily routine: one of them takes several long-haul trips a year and the other takes none.

Decarbonr uses an estimate of about 255 g CO₂e per passenger-kilometre for flying (see the plane emission factor), compared with roughly 20 g for an electrified train. On that basis, a single 1,000 km flight comes to an estimated 255 kg CO₂e. Set against the 2-tonne-a-year reference that the app uses as a 1.5°C-compatible shorthand, that one trip would be roughly an eighth of a year’s budget — and a long-haul return journey covers many times that distance.

The study does not say that flying once makes someone a problem. Its point is structural: the bulk of passenger aviation emissions comes from a small group who fly often. For an individual, the practical takeaway is simply to know which group you are in. If you fly rarely, your effort is probably better spent elsewhere; if flights appear in your year several times, they are likely to be one of your most important categories.

Growth, and the pandemic pause

The paper was written as COVID-19 grounded much of the world’s fleet; Lund University notes that global air travel fell by up to 80 percent during the crisis. Before that, industry forecasts expected global air transport demand to roughly triple over the next 30 years. The authors argue that if aviation returns to that growth path, it will come into increasing conflict with global decarbonisation goals.

For readers, the date matters: the data describe 2018. Air travel has since recovered, and the exact shares will have shifted. The underlying pattern — a small group of frequent flyers responsible for a large part of the total — is the finding most worth carrying forward.

Seeing your own share

Flights are easy to forget because they are rare events, booked weeks ahead and finished in hours. Logging them alongside everyday choices puts them back in proportion. In Decarbonr, a trip is logged by choosing one of 9 transport modes and entering a pair of cities; the app works out the distance and adds an estimate to your daily and yearly totals, next to your food and home energy.

For more on comparing transport options, see tracking your travel carbon footprint and which lifestyle changes cut the most carbon. The full list of sources behind the app is on the research page.