I don't think anyone has mentioned PVD (Providence, R.I.) yet. You walk out of the airport on the aptly named Aviation Avenue, which has sidewalks. The immediate area you exit into is mostly businesses with a few airport-oriented hotels, but several residential neighborhoods are within a ten-minute walk.
Originally Posted by
OccasionalFlyerPerson
For a lot of airports it would be getting in that would be difficult. Not the actual distance. E.g. there are houses quite close to London Heathrow, but actually getting into the airport on foot might be quite tricky. I don't know how to do it...
Eliminating pedestrian access, a few decades ago, was the reason they made TfL bus service free to anywhere within a mile or so of LHR. Now you have to walk to the bus stop of your choice along the A4 (Bath Road) and hop on the bus of your choice to finish the journey. In the other direction, go to the central bus station, pick the next bus to leave that's going east or west as you prefer, and hoof it after you get off.
For the south side of the airport, go to T4, take the walkway to the Hilton, and you can walk out from there. Not quite sure how you'd get across the Great South West Road - I've never done it on foot - but I assume it's possible. Lots of residential areas on the other side of it.