I'm a bit naive about this so please be easy on me. I would like to us my OnePass miles for a trip next summer on Lufthansa to Europe. When can I make the reservation? Will I be able to do this as soon as they join STAR in late October? I'm really locked into trying to use Lufthansa for this trip. Any other ideas would be welcomed. Thanks.

Yes, the option will be there - pending reward inventory - once CO joins *A.

No one knows exactly when. Some time after Oct 24. For a trip next summer you should have no problem going Lufthansa.

Id say you should be able to,when well that is the Million Dollar question, that as of now no one knows for sure

also unknown is how much inventory will be available to CO

I guess you could try and trade your CO miles for say UA miles as long as you can book what you want now or LH miles

Is it possible to transfer OnePass to UA or LH at this point?

no

I wouldn't exactly call it a Million Dollar question. LK has given some guidance on the issue. CO said they intend to join immediately after 10/24, but there will be a transition period of a few days. So on or about 11/1 is probably a good guess. If it deviates from that, it shouldn't be by more than a few days here or there. I don't think it'll be on 10/25, and I don't think it'll be January.

As for inventory, CO should have the same inventory that LH gives the other *A partners, which currently can be viewed via LH or the NH site.

So if you can wait 3 months, I think the OP will be fine, especially if he has reasonable flexibility in flights. LH has reasonably good availability, but if you're insistent on a particular flight, then obviously you may run into issues.

I recently had to fly SFO-SEA-FRA to get F on LH (never could get the LH nonstop SFO-FRA on my date). The UA nonstop opened up in F a handful of times, but wasn't about to give up the LH F to switch to that.

No, and it is unlikely to be available in the future.