Originally Posted by
Often1
These are not SK rules, they are US DOT rules applicable to itineraries to/from the US. Forget the whole MSC silliness.
Whatever the allowance is for the first segment, that allowance will apply throughout the itinerary. Presuming that OP is on a single ticket CPH-IAD-PHX-XXX-CPH, his CPH-IAD allowance will apply thoughout.
Note that if IAD-PHX is a connection, not a stopover, OP's bags will be checked to PHX, but he will retrieve them for CBP at IAD and then drop them. If he is stopping over at IAD, he will collect his bags and then check them in with UA when he departs IAD and pay the third bag fee to UA.
The last sentence above, amongst other things, is incorrect. Star Golds on IAD-PHX get three free bags of up to 32kg each.
The free checked bag allowance I get as an economy class Star Gold on EWR-FRA-CPH-IAD-PHX/MSP/ORD/MIA is 3 bags.
MSC rules may be applied to multi-carrier itineraries to/from the US, depending upon what the first marketing carrier on a ticketed itinerary has stipulated -- the first marketing carrier can,
under US rules, stipulate that MSC fees apply.