This occurred many years ago but it is very clear in my memory.
It was betweem Enumclaw & Auburn going to a movie in a northeast direction.
It was dark that night with no traffic or background lights.
I saw, out of the passenger side of the car, a very very large oval object covering most of the sky.
It had colors of the spectrum shimmering around its body and a row of portholes in the center.
There was a reddish fire coming from its tail.
I signalled my husband to stop the car and he also saw it.
It was moving very slowly.
Then it took off extremely fast towards the northeast and disappeared over the horizon.
Afterward we discussed reporting this but decided not to since the government was denying everything at the time.