Question for folks who know all of the rules on using SWU certificates: I just completed an ATL-JNB flight and requested weeks prior to use a SWU. It was a certificate that expired after reservations were made, but prior to the flight. The DL agent used the cert to add me on the wait list and the cert no longer showed as 'open' online. When I got to atl, however, the agent asked I verify the cert, which I never have had a paper copy of, and I no longer had access to the details online and unfortunately I didn't think to write it down. I ended using another cert that expires next year, effectively using two SWUs. I'm not quite sure what happened here. Was the original agent wrong to apply an expired SWU? or was the problem that i need to make sure that I always write down the cert numbers? When I called DL, the agent said that you should never be asked for the physic cert information once the cert has been applied electronically, so is this a systems issue! I'm trying to figure out what I need to make this smoother in the future - I think the atl-jnb is the best use for me of these SWUs. Thank you!