I don't know if this is the right place for this question, but I didn't find anywhere better and it didn't seem worthy of a new thread.

If someone's companion pass expires on 12/31/19, and they book a flight for that day (say, to return from an Xmas vacation) with the companion, and the flight is delayed/canceled and has to be taken on 1/1/20 (or later), will the CP be honored on the rescheduled flight, or will the companion have to pay for their own ticket?