Thank you very much...
it does seem that F+ is a quite good programme... have to see, if they will stick to those nice earning rates also for cheap tickets on every new Skyteam member. Plus - I realize Air India is a partner, and I did fly them already (but I bet there is no way to claim those miles from 1998...maybe worth trying when I sign up?).
Continental has a partnership with VIrgin Atlantic, but it seems to me that their discounted flights usually dont earn any miles anyway. The advantage of Onepass is however, that I can already use the miles from one flight and use them for amtrak travel in the US while on AF I need to do at least two or three roundtrips in order to receive a free ticket.
I might sign up for one of the programmes depending which airline will be the first I fly or sth like that. Thanks again for your help

PS: I dont recall where i read this problem (someone not getting UA miles for a US flight operated by LH or some other way round - but it was here in one of the forums.