Bus: direct long distance buses around 4 PM: 15.50 by Vainion liikenne (2h20mins) or 16:00 by Onnibus (2hrs) www.matkahuolto.fi Other connections prob have 1 transfer.
Both search engines use "Helsinki airport"Edited: 04 October 2016, 13:07
It's disappointing, from a tourist point of view, that the websites posted above seem to be only in Finnish. Would have expected them to offer other language choices as well.
Figured out the English language version of them eventually!