Finnair has started weighing passengers at the departure gate to refine its weight estimates for planes before take-off.

Travellers who volunteer to be measured by the airline are weighed along with their carry-on luggage and all the information is anonymised and aggregated with no one being penalised.

In the first full three days of the trial, which started on Monday, 800 passengers volunteered to be weighed, which “positively surprised” the airline.

The data is being collected “for the purpose of aircraft balance and performance calculations that are needed for the safe operation of flights,” Päivyt Tallqvist, Finnair’s senior vice president of communications, told CNN. 

Only the member of staff at the gate will see the weight, Tallqvist added. Finnair plans to weigh 1,200 passengers for the winter season, and more for the summer.

Airlines calculate how heavy a plane will be, including people, baggage, cargo and onboard catering, before each take-off.The information is then paired with the plane’s centre of gravity, and is used to contribute towards a safe departure.

The weight of customers and their carry-on luggage is typically calculated using average weights suggested by the Civil Aviation Authority and the European Aviation Safety Authority, but airlines are also allowed to use their own data and measuring systems. 

Airlines need to refresh their measurements every five years. Finnair has been doing its own maths on passenger and baggage weight averages since 2018, so is due an update to the figures.

Finnair is taking both winter and summer readings, to accommodate for the heavier clothing needed in colder spells. The weights will be used for loading calculations for 2025 to 2030.

Korean Air and Air New Zealand both did weight surveys for the same purposes last year.