Netflights is free and simple to use. You can view all five of the weekly flights to or via Washington DC, flown by one airlines. Having them all in one place makes it easy to compare prices and find the best deal for you.
Washington DC actually has one airports.
Searching by month is the best way to get a feel for the overall cost of flights throughout the year.
It's 927 km from Chicago to Washington DC, and the flight takes around 5 hrs 50 mins. Need somewhere to stay when you get there? You can add also accommodation and car hire to your Washington DC booking on Netflights.