Each aircraft has a set maximum weight for safe takeoff. Almost everything that gets onto a commercial plane — fuel, checked-in baggage, cargo and meals — is weighed. For passengers and their cabin bags, most airlines use average data. But Finland’s national carrier Finnair said Friday that it started asking passengers this week voluntarily and anonymously hop onto a scale with their hand luggage at the country’s main airport in Helsinki.

“We will need data for both winter season and for summer season — in winter season people typically have heavier clothing, which impacts weights,” Finnair spokeswoman Päivyt Tallqvist told The Associated Press, adding that the survey would last until May.

Passengers boarding onto European and long-haul flights won’t be “penalized for their weight,” and “the numbers are kept discreet, away from prying eyes,” she added.

So far, about 800 people have joined the survey, and those who agree to take part receive a small gift — a reflective baggage tag, Tallqvist said.

“While airlines know the weight of all other aspects, the weight of customers and their carry-on baggage is calculated using average weights confirmed by the Civil Aviation Authority,” he said.

Most European airlines use official data by the European Union Aviation Safety Agency, (EASA) which shows men at a mean weight of 82.2 kg (181.22 lbs) and women at 67.5 kg (148.8 lbs).

Finnair said the weight figures will be sent to the Finnish transport and communications agency later this year and will be used for balancing aircraft and loading calculations for the period running from 2025 until 2030.

“We hope to have a good sample of volunteers, both business and leisure travellers, also this time, so that we can get the most accurate information possible for important balance calculations,” Satu Munnukka, head of ground processes at Finnair, said in a statement.

The statement said, “the collected data is not linked in any way to the customer’s personal data.”

“We record the total weight and background information of the customer and their carry-on baggage, but we do not ask for the name or booking number, for example.”

“Only the customer service agent working at the measuring point can see the total weight, so you can participate in the study with peace of mind.”

Shem Malmquist, an instructor at Florida Tech’s College of Aeronautics, told CNBC, “Three hundred people that weigh more than average can put an airplane significantly over weight, and all of our performance calculations — runway length, climb, obstacle clearance, landing distances, altitude capabilities — all are dependent on weight, among other things.”

In 2022, around 30% of adults aged 18 years and older in Canada were obese, while 35% were overweight. Although the percentage of overweight adults stayed about the same from 2015 to 2022, the percentage of obese adults in the same time period increased by about four percentage points. In 2022, there were around 8.7 million adults in Canada who were obese, while the number of adults who were overweight was over ten million.

According to US government statistics, 42% of the US population at least 20 years of age is considered obese as of 2020. In the 1960s, that number was just 10%.

Airlines have come under fire for their handling of plus-sized and obese passengers and advocates for obese people claim that airlines have shrunk the width of seats in order to squeeze more profit out of each flight.

Korean Air conducted its own weighing program in 2023, while Air New Zealand also did a weight survey last year.