ACR BA41 FLC CLRNCS BECOME CONFUSED WITH COMPANY ACFT; WITH SIMILAR SOUNDING CALL SIGN; BOTH INBOUND TO STL ARPT.

Narrative

WE WERE OPERATING AS ACR X. WHEN WE FIRST ENTERED STL APCH CTL; SAME ACR ACFT Y; TIMED TO ARRIVE AT STL WITHIN 2 MINS OF OUR SCHEDULED ARR; ACCEPTED OUR HDG CLRNC. APCH CORRECTED ACFT Y. AT THE POINT IN THE ARR WHERE WE (ACFT X) WOULD EXPECT AN APCH CLRNC; ATC ADVISED ACR X TO MAINTAIN AT OR ABOVE 3500 FT IN THE RIVER; 170 KTS TO THE OM; CLRED FOR VISUAL APCH TO RWY 30R AT STL. WE (ACFT X) REPEATED THE ENTIRE SET OF INSTRUCTIONS AND CLRNC. AT AN ALT OF 4300 FT; ATC QUERIED US AS TO OUR CURRENT ALT. WE ADVISED 4300 FT. ATC ADVISED US TO STOP DSCNT; BECAUSE WE WERE FOLLOWING INSTRUCTIONS INTENDED FOR ACFT Y. ATC THEN GAVE ACFT Y THE CLRNC WE HAD BEEN GIVEN AND 3 MINS LATER TOLD ACR X TO RESUME OUR PREVIOUS VISUAL APCH TO RWY 30R. SUPPLEMENTAL INFO FROM ACN 427997: A CLRNC WAS GIVEN; WHICH I BELIEVE TO MY FLT. MY FO READ BACK THE CLRNC; WHICH INCLUDED THE OPTION OF A LOWER ALT AND COMPLETED THE XMISSION. NO RESPONSE WAS GIVEN BY THE APCH CTLR AND I BEGAN A DSCNT FROM 5000 FT. THE FACTORS WHICH CAUSED THIS DISCREPANCY ARE OBVIOUS. FLT NUMBERS VERY SIMILAR TO ONE ANOTHER; AND LACK OF ATTN DURING THE READBACK HELPED TO CREATE THIS CONFUSION.