Not sure what is going on, but anyone with a waitlisted segment for a future flight should double check the flight. This AM, a future ticketed flight disappeared from co.com. I couldn't add it back. Called co.com support, they were able to get it back. 10 minutes later, it disappeared from current & showed up in past. Called again - CSR was able to move it back, and noted that flights with waitlisted segments are causing lots of trouble.