So to clarify, a certificate can not be used on the published expiration date? (So if it expired 11/23, travel had to be completed by 11/22?) Applied the cert to the reservation a few weeks prior to the expiration date, it was wait listed, flew return flight on the expiration date, not beyond, exactly on. That just seems different from other expiration dates, ie; medallion status good all day on January 31, but not Feb 1.