They must be. Probably not officially but Finland's in NATO now so I doubt they'd really say anything also drains are incredibly hard to track so there's plausible deniability there
But you just have to look at a map of the world to realize this must be the case Moscow is closer to Ukraine than St Petersburg.
Anyway they don't even need to fly to any countries territory necessarily, they can come in over international waters, they just need to transport through other countries.