Two parallel vasilating strings of lights flare, fade to one point, and speed off over Provincetown MAI was driving towards Provincetown from Truro (Outer Cape Cod) after dark on Route 6.At about the mid-way point of Pilgrim Lake on Route 6, looking NNE over the dunes in the direction of Race Point beach, we saw something that most resembled a lowish bi-wing plane in the dark, with a line of small green and white lights running the long way along both wings (so the plane shape was inferred from the light positions.) The lights vasilated quickly from right to left on both "strings" of lights while what they appeared to be attached to remained stationary and in place for at least 30 seconds as we approached in the car at approx. 55 mph.After approximately 30 seconds, both strings of lights started to bank and turn away towards our right, quickly and brightly flared white/yellow for a few seconds, and faded to a very small, dim, neon green point of light while making a very fast u-turn. At the end of the banking u-turn, it flew off at a slight downward angle at a very high speed, went behind the highest visible dunes, and was gone. We really have no idea what it was.