In the past, I noticed that the reference code (issued now in the name of the persons) differed from one expiration date to another ONLY by the final letter. Is this still true? I have the companion certificate that expires Jan. 31, 2005 but need to use the currently issued certificate for 2005 to book a flight. I put this new certificate in a SAFE? place, and now can't find it. I think it happened when I replaced an old desk with a new one. Do you think I could use the next logical letter for the code to call it in, while I continue to look for the physical certificate?