I live 10 miles south of the capitol building on the potomac river. Starting at about 5:30am, there are convoys of heli running low(under DCA flightpath) up to the federal area from Quantico. they frequently are in a hurry, so run at close to max speed. the rotor tips approach/exceed the speed of sound, and the cracking noise is very loud.
Another bunch is stored at Andrews, and runs up and down the beltway.
I think most are federal govt machines used to haul various dignitaries around. If they cannot do the heli, a motorcade through the city is the answer.
nothing like a major motorcade from downtown out to andrews at 5pm.