The United timetables show the following options for SEA-ORD the morning of 2/29:
6:00am UA696 to DEN, then 244 to ORD
6:00am UA31 to SFO, then 134 to ORD
6:35am UA1210 non-stop to ORD
7:02am UA5787 to ODX, then 722 to ORD
So, I plan on showing up super early and with a little 1P luck and a very friendly CI agent, hopefully I can route to ORD on something other than my original "direct" flight.