Finland-based airline Finnair is asking customers for a sensitive piece of personal information before they board flights: their body weight. 

The airline said it's collecting the data anonymously from volunteers, and passengers are not required to step on scales to fly with the airline. Those who do will not have their weights shown publicly; only the customer service agent can view the number. 

"We're collecting anonymous data from volunteers on the average weight of customers and their carry-on baggage at Helsinki Airport in February, April and May. The data will be used for aircraft balance calculations," Finnair said in a statement this week. Passengers on long-haul European flights will have the opportunity to participate in the survey, should they choose to do so. The airline is hoping for "a good sample of volunteers," it said in a statement. 

Airlines typically calculate total passenger loads based on averages to make sure aircraft loads don't exceed the plane's maximum weight limit. But Finnair wants a more precise sense of how much weight passengers add to cabins. The data it collects "will be used for future aircraft balance calculations," Finnair said. 

Airlines collect exact weight measurements for everything else on their planes, including fuel, meal and baggage. But the weights of customers and their personal belongings are typically tallied using average weights.

"Time to collect updated data"

Airlines have the option of using standard weights, defined by the European Aviation Safety Authority (EASA), or relying on their own measurements, which must be confirmed by the Civil Aviation Authority. Airlines that use their own measurements must update their data every five years. Finnair last surveyed customers for their weights in 2018.

"It's now time to collect updated data," the airline said. 

Passengers' weights are kept confidential and are "not linked in any way to the customer's personal data," Finnair head of ground processes Satu Munnukka said in a statement. "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," Munnukka added.  

In May 2023, Air New Zealand began conducting a similar survey of passengers' weights to comply with the Civil Aviation Authority of New Zealand's rules governing aircraft operations. Notably, neither Air New Zealand passengers, nor airline personnel, could see travelers' weights; the scale fed the number directly into a computer for anonymous recording.

Megan Cerullo

Megan Cerullo is a New York-based reporter for CBS MoneyWatch covering small business, workplace, health care, consumer spending and personal finance topics. She regularly appears on CBS News Streaming to discuss her reporting.