Andrews air base close by. Military chopper was probably going to or coming from there. Not sure but I don't think it was necessary to be flying that close to commercial airline flight paths. Plane fags needed.
The heli flight path is strange. Heading south, does a hard 90 degree right turn towards airport, then a hard 90 degree left turn heading south, the gradually aimed directly at the landing passenger plane. The first 90 degree right turn appears to be 'aiming' at a different landing plane.