My son his wife and I saw a silver cone saucer shaped object approach an airliner at about 25 thousand Ft then sped off!My son and I were sitting on a bench along the sidewalk in Bethany beach Delaware. My sons wife and 2 small children were window shopping. My son and I were watching 3 airplanes flying approximately 2 or 3 miles apart in a easterly directions with long contrails, maybe 20 to 25 thousand ft. The middle airplane was above us. All of a sudden we saw a silver cone saucer shaped object coming from the north east. The object approach the airplane, we thought they we going to collide. The object flew along side the airplane for maybe 2 seconds. Then speed off to the southwest for a few seconds the blinked out! We were astonished that we just witnessed a UFO.. Total time around 10 seconds. Time of day, 11:10 am..