On a rainy morning we decided to check out the airplane spotting terrace on Helsinki-Vantaa airport. The terrace is nice, it is located in the office building next to terminal 2 at Lentäjäntie 1c. The terrace itself is outdoors but there is a little indoor area as well with a wending machine. However, we could have chosen the time a bit better: there was not that much happening at about 10am. But we managed to see a few, and it seemed enough even for the little airplane fan in our family.
It is free for everyone to go to the terrace between 7am and 10pm but there are no parking places right next to it. We chose to park in P2, which was a terrible choice due to maintenance work there at the moment; took us ages to find one automate to pay for the parking. But we survived, I would suggest that you try P1 or even the expensive short term parking outside terminal 2 if you go there in the near future. A bus would be a good choice too.
The entrance to the viewing terrace is pretty hidden too (but there are signs to guide you):,