My worst experiences have been on SK and AY.

As some here have already metioned SK has no biz class on domestic flights even though it sells way overpriced tix for it. There is no warning that domestic flights are first board - best seat basis. Short haul international codeshare flights are even worse. There appears to be no warning about a codeshare and you find out about it often at boarding time only.

AY, is IMO a little better than SK on short haul international flights but if having what they consider an extra perk of cold blizzard coming through the door on their turboprop for the best seats on the plane (biz class exit row) then they better reconsider. The service is also very impersonal with FA-s ignoring English language questions/wishes. They seem to think that everyone on their planes speaks Finnish and speaking English is just a "tall-poppy" syndrome unless you are dressed in football colors and are drunk and rowdy (British football hooligan).

Their international (non trans-Atlantic) service is also very disappointing with VERY poor and impersonal service, very limited pitch, poor food, no personal monitors and even lack of blankets! I hope that I will never fly them on long haul flights again!