Originally Posted by
ac789
all the airline lounge programs I'm aware of require a same-day flight with the same alliance.
The nice thing about the SkyTeam clubs is that generally you do not need to be flying the alliance carrier - and in many cases not even have to be flying at all (if the lounges are outside of security - such as both DL and CO at SFO).
I would just pick the lounge of the airline that you fly the most.