But there is always HEL (as noticed earlier in this thread). There are a lot of jokes and advertisements mixing up HEL and hell in various ways, e.g. "Hellsinki", a heavy metal music thing.

Before a recent AY flight renumbering, you could take flight 666 to HEL on Friday the 13th and book a seat in row 13...

I would not be surprised that the flight was numbered that way as a joke: The flight was from CPH, a major hub of the competitor SK, 666 to HEL...