I'm looking to book a flight that routes FRA-ATL-SFO, with the FRA-ATL portion on LH in J, and the ATL-SFO portion in X. However, that flight has a 16 hour layover, and the ATL-SFO doesn't leave until the next day. Am I able to request to be waitlisted for a first class seat on an earlier flight and request an economy seat if the first class seats don't clear? At this moment, I'm not sure if it's worth the risk of a 16 hour layover, especially if I can only waitlist for one class...