How can I see what other flights were in the vicinity



I was flying home yesterday evening on UA 621 from Chicago to Calgary and during the flight I spotted another plane, not even 1000 ft separation from UA 621 crossing our path in the opposite direction. I am a private pilot myself so I am pretty certain this was way too close for comfort and potentially for the FAA rules as well.

I would like to check on FlightAware if there was another plane tracked and how close the two planes actually were, but I don’t know if it is possible to see the flight path of one plane and then super impose other flights paths to try and narrow down the other plane.

Any suggestions on how to do this?



If they had visual separation, it was legal and no big deal. The other guy may have been VFR.