It's kind of the most awesome aviation museum this side of the Udvar-Hazy at Washington DC-Dulles, with two main halls, one each for military and commercial. The military hall is super-interestingand yes, those are blue swastikas from World War IIbut we're really commercial aviation geeks, and so the second hall was the one for us.
A Finnair Convair 240 Metropolitan is the main attraction here, and you can walk straight through it. Make sure you have a sit and marvel at how different the seats are to the ones that likely got you to Helsinki. Also well worth a peek are the various cockpit "simulators"; by "simulators" we really mean painted wooden mockups for Finnair planes from the 1950s onwards.
Getting to the museum is a little bit tricky. There are several local buses that will take you there from Helsinki Airport for a few euros, and the bus information desk in terminal 1 is only slightly helpful at giving you the right times. Guess we #avgeeks aren't all that numerous!
There are at least two bus routes that go right past, and there should be a bus every ten minutes or so. A taxi should be around ten euros, and is easier than trying to pronounce "Suomen Ilmailumuseo" to the bus drivers, because "aviation museum" is not, surprisingly enough, in the Helsinki Bus Driver English Vocabulary Handbook. Try "museo" and making the universal movement for "airplane" with your hands.
The Aviation Museum is open every day from 10-5, with late opening until 8 on a Wednesday. Note that the exhibition halls aren't heated, so if you're there in the wintertime you'll want to bring a coat. 8 Euros entry, but you will spend more in the awesome, awesome gift shop.
[Photos; John Walton/Jaunted]