Several years ago I reported my wife and I saw s strange event in the sky. It was more what we didn't see than what we did. The report described the following incident: We were driving southbound on I-75 between Tampa and Bradenton, FL. Above us and to the right we observed two (2) jet planes that appeared to be flying in formation. The odd thing that drew my attention was the vapor trail was getting longer behind only one of the planes. The other plane appeared to be pulling its vapor trail behind it. It was only later I realized the best explanation for the event is we were watching one (1) airplane, being shadowed by a reflection of itself. The reflective surface had to be "shadowing" another plane; and was flying at the same speed. That's why the vapor trail that ended at the edge of the reflective surface appeared to be pulled behind the reflection of the plane. I reported it here after I realized that was the case. HERE'S WHY I'M WRITING YOU NOW: I still think about that event, and I just now realized that whatever reflective surface was shadowing that jet was probably doing it to prevent detection by radar. THERE WAS AN UNSEEN OBJECT FLYING IN THE SAME AIRSPACE AS ANOTHER VISIBLE AIRCRAFT THAT WOULD ALL APPEAR AS ONE BLIP ON RADAR TO AIR TRAFFIC CONTROL IN THE METRO-TAMPA AREA. I think this behavior, flying close to another craft, now seems like an attack strategy that was being utilized or tested. Without knowing what the mission was I can't even guess if that object did anything after it was out of my sight. Who knows what might be flying over us if we can't see it or detect it with radar?