A recent study by the American investment bank Jefferies estimates that the four largest American Airlines could save as much as 580 million dollars per year in fuel costs if passengers weighed less.

The study approaches the weight issue from a surprising angle, namely the impact of rheumatoid arthritis on often controversial weight loss drugs such as Ozempic and Wegovy.

At the same time, however, the study fuels the climate debate over whether travelers should now pay extra under a ‘pay per kilo’ model, the Frequent Flyer Levy, or a personal carbon budget.

Obsessed with minor weight savings

Obesity treatments are popular, as evidenced by the success and controversy surrounding drugs such as Ozempic, Wegovy, and Mounjaro. It also inspired the American investment bank Jefferies to look at the cost savings for American airlines if society were to become lighter.

Airlines are currently obsessed with small weight savings, as evidenced by the dispute between O’Leary and Musk regarding the impact of weight on onboard Wi-Fi.

But they are also using thinner paper for their in-flight magazines, opting for lighter forks and knives, and filling water tanks to a lower level. According to Jefferies, however, the emergence of GLP-1 drugs, both diet pills and injections, has a much greater impact than all these small technical interventions combined.

The study’s calculations show that if the average passenger weight decreases by 10%, or about 8-9 kg, the total weight of an aircraft, such as the Boeing 737 Max 8, would be reduced by about 2%.

For the four largest American airlines, American Airlines, Delta Air Lines, Southwest Airlines, and United Airlines, this would result in a combined saving of no less than 580 million dollars per year in fuel costs.

A decrease in passenger weight also immediately increases airlines’ earnings per share by an estimated 4%. This is because fuel often accounts for around 20% to 25% of an airline’s total operating costs.

Ticket by weight

Jefferies is obviously not the only one who has already concluded that weight is the biggest enemy of efficient flying. But while the investment bank suggests that the industry will quietly benefit from the medical trend of people becoming lighter due to obesity treatments, Belgian professor Damien Ernst (University of Liège) has previously proposed that heavier passengers should pay more for their tickets.

Currently, passengers pay a fixed rate for their seat, regardless of whether they weigh 60 kg or 120 kg or carry 5 kg or 20 kg of hand luggage. But every kilo requires extra energy to stay in the air and move forward. According to Ernst, this is economically and ecologically illogical. Those who add more weight to the flight cause more emissions and should pay for it.

Discriminatory

However, Ernst’s proposal, which critics have dubbed the ‘fat tax’, raises several ethical questions. After all, your weight is largely beyond your direct control, as genetics play a significant role.

Research on the heritability of body weight, often measured by BMI, shows that genetic factors play a significant role. In other words, you are being financially penalized for a physical characteristic that you did not ask for.

Regardless of the discriminatory aspect of such a measure, whereby heavier passengers would have to pay more than lighter ones, weighing passengers at the gate is also considered humiliating by many.

Precedents

Yet it has already happened. In early 2024, Finnair began weighing volunteers at Helsinki Airport. Not to make people pay more, but to refine internal calculations of the aircraft’s total weight.

Air New Zealand also conducted a similar study in 2023 on the average weight of passengers, including hand luggage, to more accurately plan fuel requirements. Korean Air has also introduced weighing for statistical purposes.

Samoa Air even introduced the ‘Samoa Air Tax’ in 2013, under which passengers paid per kilo of body weight and per kilo of baggage. But the now-defunct Samoa Air was a small, regional airline that flew tiny aircraft, where weight distribution was critical to the aircraft’s balance. Plus, as on other islands in the Pacific, the percentage of obese people is much higher, as is the average weight of passengers in that region is much higher than the global average of 84 kg – a matter of genetics, nutrition, and culture.

Focus on seat width

Instead of weighing everyone as they did in Samoa, many airlines now look at seat width to regulate weight and comfort.

In the 1970s, the average width of an Economy seat was around 45-46 cm. Today, that has dropped to 41-43 cm for many airlines. At the same time, the average width of human hips has increased. This means a passenger’s ‘physical footprint’ is more often outside the boundaries of their ticket.

Some experts suggest translating Ernst’s vision into different seat sizes within Economy class, ranging from small and standard to extra-wide. That way, passengers do not pay for their weight, but for the space they occupy.

Many American airlines have a rule that if you cannot lower the armrests or fasten your seatbelt with just one extension, you must book a second seat. Sometimes you get the cost of the second seat refunded if the flight is not fully booked, but it is essentially an indirect weight tax.

It is interesting to note that aircraft manufacturer Airbus has already applied for a patent for a bench system, a continuous bench instead of individual seats. A family with three small children would then take up less space than two large adults on the same bench and therefore must pay less.

‘Beam me up, Scotty.’

Another problem with Ernst’s tax is that a heavier person who flies to Spain once a year would pay much more than a slim person who flies from Antwerp to London every month for a city trip in their private jet.

Research also shows that a small group is responsible for the majority of aviation emissions. A progressive tax, whereby your ticket becomes more expensive the more you fly, therefore seems more socially just.

And teleportation à la Star Trek’s “Beam me up, Scotty” is still a long way off, although the hyperloop comes closest to ‘beaming’ in terms of feeling. However, a high-quality digital avatar that allows you to travel virtually for business meetings, for example, may become the standard for zero-emissions travel in the future.