A B727 FLC ACCEPTS A CLRNC INTENDED FOR ANOTHER ACR FLT WITH A SIMILAR CALL SIGN. ATC CATCHES THE ERROR AFTER THE WRONG FLT HAS BEEN INTO ITS DSCNT FOR OVER 5000 FT NEAR OXI; IN.

Narrative

AS FLT ABCA (WITH FLT ADCA ALSO ON FREQ) WE FIRST RECEIVED A CLRNC TO CROSS 30 NM E OF KNOX AT FL250; 300 KIAS. AT 35 NM E OF KNOX; WE RECEIVED FURTHER CLRNC TO 17000 FT. WE (CAPT) READ THIS BACK. THEN; WE WERE TOLD TO MAINTAIN 320 KIAS. SEVERAL MINS PASSED; AND WE HEARD ATC QUERY 'FLT ADCA' REGARDING THEIR ALT CLRNC; '...CROSS BEARS AT 17000 FT.' FLT ADCA SAID THEY 'DIDN'T RECEIVE THE ALT; ANOTHER ACFT MAY HAVE READ IT BACK.' I SAID TO THE CAPT; 'I BET THAT WAS US.' SURE ENOUGH; ATC QUERIES US TO OUR CLRNC; WHICH WE AGAIN READ BACK AS 17000 FT. ATC HAD US STOP OUR DSCNT AT FL210 -- TOO LATE; AS WE WERE ALREADY PASSING THROUGH FL193. I ARRESTED DSCNT AND CLBED BACK UP TO FL210. THIS IS A CASE WHERE OUR READBACK WAS NEVER CONFIRMED. AND EVIDENTLY; THE OTHER CREW ON ADCA 'MISSED' THE CALL SIGN (IF; INDEED; THE CTLR MADE NO ERROR). I BELIEVE ATC CALLED THE OTHER FLT OUR NAME; AND THE RAPID FIRE COM COUPLED WITH SIMILAR CALL SIGNS (AND MOST IMPORTANTLY LACK OF VERIFICATION OF READBACK) LED TO THIS POTENTIAL INCIDENT.