Narrative:

Upon arrival in atl, a deplaning passenger reported that we had a near miss. He insisted that we were aware of the other aircraft because we 'throttled back to avoid a collision' about 15 mins before arriving in atl. We received no TCASII alerts en route and were not aware of any traffic conflicts. I immediately called company in atl to notify the chief pilots office and query atl approach. ATC was unaware of any sits involving a lack of separation with other IFR or known VFR traffic. Passenger insistent on notifying FAA and was encouraged to do so. Location of incident estimated based upon passenger testimony of power reduction. Power was brought to idle to slow from best forward assigned airspeed to 210 KIAS assigned at about atl 133 degree radial, 20 NM on STAR.

Related reports:

Google
 

Original NASA ASRS Text

Title: PAX ON A B727 RPTS AN NMAC TO THE FLC AFTER LNDG. FLC OR ATC HAD NO KNOWLEDGE OF SUCH AN INCIDENT.

Narrative: UPON ARR IN ATL, A DEPLANING PAX RPTED THAT WE HAD A NEAR MISS. HE INSISTED THAT WE WERE AWARE OF THE OTHER ACFT BECAUSE WE 'THROTTLED BACK TO AVOID A COLLISION' ABOUT 15 MINS BEFORE ARRIVING IN ATL. WE RECEIVED NO TCASII ALERTS ENRTE AND WERE NOT AWARE OF ANY TFC CONFLICTS. I IMMEDIATELY CALLED COMPANY IN ATL TO NOTIFY THE CHIEF PLTS OFFICE AND QUERY ATL APCH. ATC WAS UNAWARE OF ANY SITS INVOLVING A LACK OF SEPARATION WITH OTHER IFR OR KNOWN VFR TFC. PAX INSISTENT ON NOTIFYING FAA AND WAS ENCOURAGED TO DO SO. LOCATION OF INCIDENT ESTIMATED BASED UPON PAX TESTIMONY OF PWR REDUCTION. PWR WAS BROUGHT TO IDLE TO SLOW FROM BEST FORWARD ASSIGNED AIRSPD TO 210 KIAS ASSIGNED AT ABOUT ATL 133 DEG RADIAL, 20 NM ON STAR.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.