Massive Triangular Vessel with Dim Blue Glow to its underbelly

October 5, 1992 or 1993 (been awhile) driving from Palm Springs to Phoenix for my birthday.  We were on I-10 at approximately 10:30pm heading east( about half way to Phoenix).   A large triangular "vessel" passed over us.  It was also HUGE. Bigger than a Stealth.  Again like others have stated, it was moving so slow and making no noise at all....moving too slow to be flying like an airplane.  And was about 300 feet above us.  It was not smooth on the underneath side, you would see into different areas of it, due to the fact that there was a dim blue glow to its underbelly.  There were other cars behind us and I am sure they saw what we saw.  We both turned to each other and said "  No one will believe us!"
Witness indicates that the date of the sighting is approximate.  PD