Triangular craft w/ flashing lights in 1976

On said date, my friend and I were walking home from the movies.  He looked up and became transfixed, not moving or saying anything.  I asked what was he looking at and he just pointed straight up and said, "Will you look at that."  Directly above us, fixed among the stars, was an extremely large, silent triangular craft that seemed to just float along.  Intermittantly flashing lights travelled in irregular patterns, to and fro, blue and red with a smidge of yellow in the mix.  We both stood in the roadway and watched it hover and move in a straight line until it passed from sight over the horizon of pine trees.  We spoke only of this to ourselves for the longest time, fearing ridicule.  No one tends to believe two 16 year olds with overactive imaginations.  As an epilogue to this strange event, one night my wife and I were watching Unsolved Mysteries in the mid-'90's and Robert Stack did a report of strange triangular craft seen in the SE Virginia corridor and, upon seeing their re-creation of events, I bolted from my chair and hollered out, "That's it!  That's what we saw back in high school!"  My father-in-law, an ex-US Airforce officer, was sitting on the couch and had been in an animated state up to that point.  Upon my recognition of this craft, he stopped all he was doing and then just stared at me for about a half minute.  He then arose from his seat and walked--zombie-like--from the room.  He refused to speak of it to me and, from that moment on, I knew what we had seen was not open for discussion.  This told me the Air Force already knew all about it.