Not necessary information: how to talk to DL about missing a flight due to an hours-long traffic closure is pretty general and applicable to anyone, on the way to any airport. but, since you're nosey:

SLC. Only a daypack as carryon... Semi-truck crash and fire in Parleys Canyon, Interstate 80. Closed the road for over 4 hours. Traffic backed up all the way back up the canyon. No way to turn around/move. Guest departed hotel before the crash - crash happened while he was enroute. Please don't say they could have turned around or something else. I had friends who live down in SLC stuck in the same jam and couldn't get home for hours.