While driving south on a dirt road aproxamently 3 miles west of Burlington, I observed a very large aircraft that appeared manmade flying very slowley at an extreme low altitude. It was flying in a West-NorthWest direction and passed over the road directly in front of me. The craft appeared to be a jet engine design though it produced no visible exhaust or flame. It was also completely silent, and I was close enough that I should have heard an idleing engine or something. it was moving very slow, maybe 15 MPH. It appeared to be maintaining a steady altitude. It was larger than a standard American fighter jet. the front end was long and round. the wings appeared to be set back towards the back of the fuselage. The Color appeared to be a black or dark green. The overall styling looked Vietnam era or older. This is a rural area and the only low flying aircraft are usually crop dusters.The weather was cool and very windy, but sunny.