I've looked at Alaska's baggage policy page and it appears they will through check on separate tickets where they have interline baggage agreements, but it isn't clear as to which carriers this applies to. Due to quirks in AA's system as well as potential unavailability of award seats on AS, I have SAN-SEA booked on an Alaska paid ticket and SEA-LHR-NCE on AA miles. Same day - reasonably long connection in the case I need to recheck. That said, will AS be able to through check my bags from SAN?