Originally Posted by docbert

Can't speak for the OP, but for some airlines this is the correct way to do it (well, ignoring the Koru part). For example, with SQ in order to get full benefits you need to join KrisFlyer, and register your other FF number (eg, UA) against your KrisFlyer account. This gives you the ability to credit to (and get status from) the other airlines program, whilst still getting the benefit of having a KrisFlyer account (eg, free onboard wifi).