Triangle-shaped craft w/3 lights, moving fast

Looking up at the SW sky while on security duty next to the airport, sky was clear of clouds, stars visible, and then observed a suspicious unidentified craft travelling in a NE direction. I have never seen an aircraft of this configuration or one at that altitude before, and I have looked at many typical aircraft types in those skies. This craft was a triangular shape--I could barely make out the outline against the dark sky--and it had 3 solid white lights on the bottom side (one at each point of the triangle). I suspect it was at about the altitude that single engine small planes are at, but there is no way for me to know; and the size of it is unknown, but I am guessing it was very large. It was travelling at a high rate of speed because it was only visible for roughly 6 seconds before it went out of sight into the light pollution in the NE sky. No engine noise was heard like you would expect from a large jet engine and for a craft going that fast.