B737-800
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 200; Flight Crew Type 16500
Communication Breakdown
Conflict NMAC; Flight Deck / Cabin / Aircraft Event Passenger Misconduct
General None Reported / Taken
Aircraft; Human Factors
During deplaning; a passenger approached me and asked about an aircraft that we got very close to. I responded that I was unaware of any abnormally close aircraft during our flight. He responded that we had gotten about 200 ft. away from what he thought was [another] aircraft. I asked him where he thought this occurred and he said; 'somewhere over ZZZ I think'. I assured him that our minimum separation enroute was 1;000 ft. and that we had no close encounters with any other aircraft. He claimed he knew exactly what 1;000 ft. looked like and that the aircraft he saw was definitely 200 ft. away. I asked him if he knew what kind of aircraft it was; hoping to explain that large aircraft appear closer but he said he had no idea what type of aircraft it was; just that he thought it was a (other carrier) aircraft. I again mentioned that we had not come closer to any other aircraft than the standard separation of 1;000 ft. We had no traffic alerts nor any other TCAS has events for the entire flight. The passenger left the jetway after this short conversation.
B737 Captain reported that a deplaning passenger expressed concern that during cruise another aircraft had passed closeby; with less than 1;000 ft of separation; although the separation standard had been met during flight and that no TCAS events had occurred.