A B727-200 ACR FLT NUMBER IS CONFUSED WITH A DEP A320 WITH SIMILAR SOUNDING CALL SIGN. THIS CONFUSION IS CARRIED ALL THE WAY TO THE ZOB CTLR; STARTING AT DTW; MI.

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FLT ABC WAS OUR FLT NUMBER. A SIMILAR CALL SIGN ALSO ON FREQ. WE HAD EXPECTED DEP CLRNC TIME FOR EWR WHICH EXPIRED ON TAXI OUT. GIVEN TAXI TO HOLD BAY. RELEASE TIME 15 MINS FROM NOW. WE SAT 5 MINS; THEN TWR POSITIONED US TO HOLD SHORT OF RWY 3C. AFTER 2 OR 3 DEPS WE HEARD 'ABC TAXI INTO POS AND HOLD.' WE COMPLIED. THEN WE HEARD 'ZBC CLRED FOR TKOF.' I HAD THE FO QUESTION THE CTLR 'ZBC OR ABC?' THE ANSWER WAS ZBC. WE STATED THAT WE WERE ABC. 'WHAT IS YOUR POS?' WE ANSWERED 'IN POS ON RWY 3C.' CTLR ASKED 'ZBC WHERE ARE YOU?' 'WE ARE #1 SHORT OF RWY 3C ON TXWY M.' (THAT ACFT WAS DIRECTLY ACROSS THE RWY FROM US WHEN WE WERE INSTRUCTED TO 'POS AND HOLD'.) AFTER THE TWR SORTED OUT THE SIT; WE WERE TAXIED DOWN THE RWY AND BACK TO THE HOLD BAY. WE WERE RELEASED 7 MINS LATER. A FREQ CHANGE WITH ZOB REVEALED 'ABC; NO. I'M LOOKING FOR ZBC. ABC YOU NEED TO BE ON 134.12.' OBVIOUSLY; SIMILAR SOUNDING CALL SIGNS ARE ONGOING PROB WITH ATC. OUR SIT AGGRAVATED BY THE FACT THAT Z AND A ARE SIMILAR SOUNDING OVER THE RADIO. I'M GLAD I CAUGHT THE ERROR WHEN I DID. I CAN ONLY IMAGINE THE CONSEQUENCES HAD I GOTTEN AIRBORNE!