Massive Black Triangle over Salisbury

It was a hot night.  Myself and two other friends were standing on one of my friend's front porch.  I had grown bored of the conversation and was looking at the pine trees to the south.  I was wondering when the city had put a new arc light there.  The color was the same yellow and the brightness the same intensity.  I soon realized that this light was moving.  
The object then went over out heads.  It was a massive black triangle.  My fist at arms length would not have covered the object.  I measured it using my clenched fist and the back end of the triangle was four fists wide.  At the front of the triangle were two huge lights that projected beams into the night, and then down the front two sides were three smaller lights about the brightness of Jupiter in the night sky.  
The object moved slowly south to north, and what sounded like a huge diesel engine could be heard.  Knowing of the missing time phenomenon, I had checked my watch when I had realized what! I was seeing and then after.  
Four minutes had passed.  I know that the object was a solid triangle and not a boomerang shape because the stars were blacked out.  Later, I would say the way it moved reminded me of a blimp.  
One item of note is the direction it traveled.  Almost all of the air traffic in Salisbury travels east and west; Pittsburgh to Baltimore or New York or DC.  I found it odd that it was traveling south to north.
Witness indicates that the date of the sighting is approximate.  PD