LVL CHG:
Aircraft rotation in SAS always used to be according to tax benefits. Something about fuelling an a/c tax-free in one Scandinavian country when flying to destinations outside the premises.
Since the 90'ies, with leasing instead of ownership of a/c, SAS shifted registry of their fleet between the three scandinavian countries, presumably to gain tax benefits. This can be verified by looking at the Registry of Aircraft in either country. "In-and-out" - wow.
Edited: These are only personal observations from reading the registry over the years.
