With all the rumors of change going on I will put a big * by this.
DCA/BWI/IAD are the same place so if you have MCI-ORD-IAD on an award you can change, same-day, to MCI-ORD-DCA without penalty. If you decide to take AA or US or whoever from WAS-NYC, UA at Kansas City can tag your bag the WHOLE way no need to pick it up and transfer it yourself. Your 2nd airline BP is the only thing you'll need to aquire.