Originally Posted by CPH-Flyer

(2) I guess it is all about upgrades... So you would need the numbers registered well in advance. Some airlines' systems allow multiple FFP on one booking, some does not I don't know where SK and UA are in that scale But try, and let us know how it works out. I would do this by accessing the booking first from SK to get your EB number in, the try to see if you can modify the UA legs only from their website.