Richard from DC on 9/12/2020 4:55:03 PM:
It's a piece of cake. You just drop down to the river and follow it, bike paths all the way, to the 14th Street Bridge at the Jefferson Memorial. When you cross the bridge, you cloverleaf down to another bike path that will take you to the airport. Maybe two miles from the end of the towpath to the bridge, less than a half mile over the bridge, and a mile to the airport. But the rental car places are on Highway 1, which is west of the bike path. Cell phone GPS would help you find everything.
Also, at about Mile 1, you'll see an asphalt bike path at Fletcher's Boathouse. Finishing the last mile on that puts you right along the river and the bike path that goes to the 14th Bridge. Follow the airplanes if all else fails.