Narrative:

Our flight was vectored from the FRIZN4 RNAV STAR arrival to a 20 mile final for runway 35L at sdf. When asked by ATC; we called the regional jet (rj) 5 miles ahead 'in-sight'. Our flight was cleared for the visual 35L approach behind the rj and instructed to maintain 170 knots until a five mile final. At approximately 16 miles (irli DME); we received a TCAS traffic advisory (TA). It was apparent to my first officer; by visually looking out his right window; that an all-white aircraft was coming ever closer to our airplane. The aircraft was at an altitude just a little lower than our own. TCAS indicated the aircraft was only 500 feet below our aircraft. Upon querying ATC; we were advised the aircraft was 'landing on 35R' and that it was 'working his way back'.the total horizontal distance between our two aircraft was approximately 200 feet. We never received a GPWS alert of any kind or a radar altimeter distance; so I don't actually know if our airplanes ever overlapped. At one point; when our vertical separation from the aircraft on TCAS indicated 600 feet; it actually showed he was in a climb; as displayed by an up-arrow next to a negative 6 (-6). Again; my first officer asked louisville approach control (120.3) what they wanted us to do. My first officer advised louisville approach control we lost visual contact with the aircraft as it passed under our airplane. Louisville approach control advised us to maintain 4;000 feet (MSL). I continued to fly the airplane and monitor the situation/ discussion with ATC.when it became apparent to ATC the aircraft had started back toward runway 35R; we were re-cleared for the visual approach to runway 35L; 'so long as we could descend to the runway in time.' we met our company's stable approach criteria before reaching 1;000 feet MSL and landed uneventfully.I believe the pilots of the other aircraft lost situational awareness and mistook sdf runway 35L for runway 35R. This serious blunder put a lot of people and equipment in jeopardy. In my opinion; louisville approach control seemed somewhat nonchalant about the whole situation. Louisville approach control almost appeared reluctant to challenge the other aircraft flying through the 35R localizer; to react to the transgression of the 35L approach corridor by the other aircraft or to issue breakout instructions to either aircraft.

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Original NASA ASRS Text

Title: Air carrier flight crew reported a near miss with another air carrier while on approach to SDF.

Narrative: Our flight was vectored from the FRIZN4 RNAV STAR arrival to a 20 mile final for Runway 35L at SDF. When asked by ATC; we called the Regional Jet (RJ) 5 miles ahead 'in-sight'. Our flight was cleared for the visual 35L approach behind the RJ and instructed to maintain 170 knots until a five mile final. At approximately 16 miles (IRLI DME); we received a TCAS Traffic Advisory (TA). It was apparent to my First Officer; by visually looking out his right window; that an all-white aircraft was coming ever closer to our airplane. The aircraft was at an altitude just a little lower than our own. TCAS indicated the aircraft was only 500 feet below our aircraft. Upon querying ATC; we were advised the aircraft was 'landing on 35R' and that it was 'working his way back'.The total horizontal distance between our two aircraft was approximately 200 feet. We never received a GPWS alert of any kind or a radar altimeter distance; so I don't actually know if our airplanes ever overlapped. At one point; when our vertical separation from the aircraft on TCAS indicated 600 feet; it actually showed he was in a climb; as displayed by an up-arrow next to a negative 6 (-6). Again; my First Officer asked Louisville Approach Control (120.3) what they wanted us to do. My First Officer advised Louisville Approach Control we lost visual contact with the aircraft as it passed under our airplane. Louisville Approach Control advised us to maintain 4;000 feet (MSL). I continued to fly the airplane and monitor the situation/ discussion with ATC.When it became apparent to ATC the aircraft had started back toward Runway 35R; we were re-cleared for the visual approach to Runway 35L; 'so long as we could descend to the runway in time.' We met our company's stable approach criteria before reaching 1;000 feet MSL and landed uneventfully.I believe the pilots of the other aircraft lost situational awareness and mistook SDF Runway 35L for Runway 35R. This serious blunder put a lot of people and equipment in jeopardy. In my opinion; Louisville Approach Control seemed somewhat nonchalant about the whole situation. Louisville Approach Control almost appeared reluctant to challenge the other aircraft flying through the 35R localizer; to react to the transgression of the 35L approach corridor by the other aircraft or to issue breakout instructions to either aircraft.

Data retrieved from NASA's ASRS site 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.