Low level, high speed flyby

A friend and I were driving down the West side of Camano Island on SW Camano Drive. Approximatly one mile South of the Elger Bay grocery store, an object crossed above the road at a height of no more than 50 feet above the treetops at a distance of about 300 yds in front of us. The object was low enough that I was only able to view it in profile. It had a wedge-shaped profile with a pointed nose. The object glowed with the luminous intensity of a fluorescent light. I was able to observe a glow on the trees and ground that helped me identify the distance as the object passed over. The object did not emit any sound that I detected. The size of the object appeared to be a wedge about 80 feet long and 20 feet high at the tail, viewed in profile. There was a small dark area about fifteen feet behind the pointed nose that may have been a window.
As a helicopter pilot in Vietnam, I had developed the habit of taking a mental snapshot of an event, then analyzing it during the following moments, even while engaged in other activities. Due to this habit, I was able to compare its speed to my memory of a Phantom F-4 that I knew was flying at 600 knots at a similar range. Based on this comparison, I would estimate the speed of the object to be three times that of the F-4, or about 1800 knots.
Date is approximate.  We will invite the witness to try to establish the exact date of the sighting.  PD