This is possible, but not likely. As I said, I saw the light from behind and to the left of the aircraft. I would guess their altitude to have been low enough to be in a landing pattern, but not low enough to be on an approach. Planes on approach to Reagan National often pass over the house low enough to distinguish the airline.
Those afterburners sure are purty.
This type has an extra identification light, about the size of a landing light. It is mounted on the left side of the nose, pointing left slightly fwd and slightly up. The light allows the F-16 pilot to intercept another aircraft and slide in behind and low, out of veiw from the other pilot. The F-16 pilot then turns on the ID light and can get a good look at the tail markings and numbers of the intercepted aircraft.
You probably did see an intercept as the Washington area is a very high security area under constant airborn CAP. Aircraft are intercepted and identified on a routine basis. You probably saw the ID light reflected off the intercepted aircrafts' tail.