The carrier doesn't want to start charging passengers based on their weight but simply asked 2,000 passengers to step on a scale prior to boarding in an attempt to verify the accuracy of its planes total weight.
The weigh-ins, which took place this week, were totally voluntary and carried out at Helsinki Airport.
Finnair did this to check its unique passenger population against weight estimates provided by the European Aviation Safety Agency, according to the airline's communications director Päivyt Tallqvist.
Passengers who volunteered boarded a scale with their outerwear and carry-on luggage. Their weight was only visible to the airline clerk, Tallqvist told HuffPost.
Finnair, like many airlines, relies on estimates but passenger weights can vary by nationality, ticket class and time of year.
Finnish passengers usually contribute more weight in winter due to their bulky coats, Tallqvist said.
"We want to see if the data we're using for calculations is accurate," Tallqvist said.
"We use them for every flight, and they're important for the aircraft's performance. When you explain this to [passengers], they understand."
World's weirdest airlines
World's weirdest airlines
Not all airlines offer standard flight experiences. Travellers looking for fun or unusual services can enjoy the most unexpected journeys across the skies with the world's wackiest airlines.
Whether you and your travel companion are 'cuddlers' or you're a social media junkie, these are the weirdest and unique airlines offering unconventional flights...
This South African low-cost airline is known for offering one of the most entertaining in-flight services. The brand was built on South African humour and has a fleet of 12 bright green Boeing 737s. Its tongue-in-cheek style includes in-flight instructions such as, "Please note we do not accept unwanted mother-in-laws or children". In 2011, the airline offered bride-to-be Kate Middleton's family a herd of cows as a gift.
Ideal for passengers who have trouble relaxing on a plane, Air Malta's Sky Spa offers the unusual service of free pampering on short-haul flights - and for economy passengers. Two professional therapists welcome flyers with beauty product samples and pamper them with the complimentary treatments, which include hand, feet and neck massages as they listen to relaxing music.
When it comes to themed aircraft, EVA Air wins for its colourful Hello Kitty jets that are designed to make flying fun and give passengers an experience to remember. Adorned with images of Hello Kitty and her friends, the planes are not the only feature cartoon fans can enjoy. At check-in, passengers receive Hello Kitty boarding passes and on-board, the cabin crew wears Hello Kitty uniform. The quirky flights are available on selected routes, including Taipei to Paris, Taipei to Singapore and Taipei to Chicago.
The flights are no longer available and after hosting a mid-flight dance by bikini-wearing beauty pageant contestants in 2011, Vietnamese no-frills airline VietJet Air was fined 20m dong (£611) by aviation authorities. The company said it wanted to capture a "holiday atmosphere" for its new flight route to Nha Trang. Nguyen Trong Thang, chief inspector of Vietnam's civil aviation body, said the carrier "had violated the local aviation regulations by organising unapproved show on a plane".
If you can't get enough of social media, KLM is the airline for you. The carrier's Meet & Seat service allows you to find out who will be on your flight, view other passengers' Facebook or LinkedIn and see where they are sitting. It's a fun way to find out about interesting people who will be on board. But for those who find it creepy, you can opt out of having your social media accounts linked with your flight bookings - phew!
Passengers who can't keep their hands off their travel companions will adore Air New Zealand's Economy SkyCouch, also known to some travellers as 'cuddle class'. The SkyCouch is a row of three seats that are like having your own couch on the plane. Passengers can create a flat, flexible space to use however they like and it even has an extension belt for when you want to lie down and armrests that disappear into the back of the seat.
Pokémon fans far and wide can fly in a themed jet with ANA on routes such as Tokyo to Frankfurt and Tokyo to Paris. The planes feature characters including Pikachu, Togepi, Mew and Snorlax, with in-flight treats ranging from juice served in Pokémon cups and flight attendants wearing colourful poké-aprons.
Can't decide where you want to fly? Eurowings offers mystery flights at a fixed price. The Blind Booking service allows you to choose a departure airport and what sort of trip you're in the mood for (gay-friendly, shopping and culture are some of the options). If there are locations you'd rather not visit, you can pay five euros per undesirable destination to exclude these from the selection. As soon as your booking is complete, you'll find out your destination.
Low-cost airline WOW air is so supportive of LGBT rights and advancing support of the community in the US that it introduced a new aircraft name TF-GAY to its fleet in 2016. The carrier, known for its bright-purple planes, launched the new Airbus A330-300 to serve its Reykjavik to San Francisco route. WOW air's CEO Skuli Mogensen said: "Since day one, we’ve emphasised joy and friendliness in our services because we want everybody to feel welcome in the WOW family. And we think TF-GAY fits right in with our modern family concept."