The furthest airport from DC in Maryland is an hour flight vs a nearly 3 hour drive or train trip. Also, I would be interested in knowing if this "destination" is final destination or layover. DC is a major hub -- I've had layovers there many times.
Maryland has only three commercial airports - BWI, Salisbury/OC, and Hagerstown. The smaller two, combined, have flight numbers less than 1% of BWI's traffic. And, there aren't any direct flights from BWI to either of Washington's other two airports. Since BWI is a Southwest hub and by far the airport's largest carrier, I would think another SWA hub city would be a candidate.
I live in Virginia and I have never seen any flight to and from Toronto ever before. Can someone please explain this. I would have said New York, Washington, Charlotte, or Atlanta.