Ospreys are primarily used by Marines for troop and cargo transport and Air Force Special Operations Command (AFSOC) for special missions. The Marine base in Quantico, just south of DC, is the home of HMX-1, which is the squadron designated to move President and staff around. I wouldn't think it is uncommon to see these flying around DC. I would be more worried about armed Ospreys flying around the city. If they are armed there would be a 50-cal or minigun hanging out the back since the Osprey has no forward or side firing weapons.

Edit: HMX-1 aircraft to move the President and staff are painted that green and white scheme like the paint on Marine-1 (helicopter that lands at White House all the time). Tactical aircraft are painted tactical gray.

Ospreys are primarily used by Marines for troop and cargo transport and Air Force Special Operations Command (AFSOC) for special missions. The Marine base in Quantico, just south of DC, is the home of HMX-1, which is the squadron designated to move President and staff around. I wouldn't think it is uncommon to see these flying around DC. I would be more worried about armed Ospreys flying around the city. If they are armed there would be a 50-cal or minigun hanging out the back since the Osprey has no forward or side firing weapons.