I think my guess is Air Baltic with their CS300s purely on the basis a few times it has now been mentioned that saying the aircraft type would give the airline away. I don't think there are many aircraft types that would do that and this is the main one that I can think of. Plus, they already have a decent number in their fleet (which might be surplus at this time if they keep some of their old fleet) and they would be a good size for a more frequent schedule than other low-cost operators may use.