I was outside of the office tower where i work, having a smoke break on the street with a colleague and he pointed to the sky and commented how two planes (one flying south to north and the other north to south) looked like they were headed directly toward each other. they both looked like standard commercial jet airliners but they seemed to be too close and aiming at each other. they both appeared to be the same size in the sky, at the same high altitude and both had long bright white contrails of equal length. i turned back toward my colleague momentarily as he turned his head away to light his cigarette. i continued with our conversation when he looked back up and said one of the planes was gone. i turned and looked back up in the same direction in the sky and the plane flying from north to south had completely vanished along with it’s long white contrail. we had taken our eyes off of it for only about five seconds. it was daytime, it was a clear blue sky and two planes and contrails were clearly visible and within a few seconds one of them had vanished along with its contrail. the second plane (flying south to north) continued unaffected along its course. we were both dumbfounded. i searched online for any accounts of today’s event but found nothing. i’m reporting this to your site in the hopes that other people may have done the same in order to find an explanation. thank you for your time.