I have a slightly different question along the lines of this topic. My award itinerary has me traveling first leg Alaska and then the second and third legs on British Airways.

I was wondering if it is possible to do an online check-in with Alaska for the entire route or does one need to check-in separately online with BA to pick seats (of course BA doesn't let you pick seats until 24 hours out....)? Has anyone successfully checked in all the way through Alaska onto British Airways? Or do you need to do all this at the airport only?