WHEN THE CTLR ORDERED THEM OFF THE RWY; AN ACR FLC DISCOVERED THAT THEY HAD PICKED UP A POS AND HOLD CLRNC THAT WAS MEANT FOR ANOTHER AIRLINE WITH A SIMILAR SOUNDING CALL SIGN. ACTUALLY; THE OTHER ACR'S NAME WAS SIMILAR; BUT THE FLT NUMBER WAS IDENTICAL.

Narrative

WE WERE ACR XEX (DTW-TPA). AS WE APCHED THE END OF RWY 21C FOR TKOF; WE HEARD THE TWR SAY; 'ACR XEX; TAXI INTO POS AND HOLD RWY 21C; TFC 7 MI FINAL.' WE ACKNOWLEDGED WITH; 'ROGER ACR XEX; POS AND HOLD RWY 21C.' AFTER LOOKING AT THE FINAL AND SEEING AN ACFT ABOUT 7 MI OUT; WE TAXIED ONTO RWY 21C. AT THIS TIME THE TWR SAID; 'ACR XEX; THAT WASN'T FOR YOU; TAXI CLR.' WE CONTINUED ACROSS THE RWY TO THE E PAD AND TURNED AROUND. THE TWR THEN SAID; 'WE MEANT TO SAY RWY 21L.' AN A320 LANDED. THE TWR THEN SAID; 'ACR XEX TAXI INTO POS AND HOLD RWY 21C.' FORTUNATELY; WE WERE SLOW TO RESPOND (WE WERE NOW SUFFICIENTLY PARANOID) AND WE HEARD ANOTHER ACR XEX ANSWER AND TAKE THE RWY. HE WAS RIGHT. THE TWR WAS NOT CAREFUL ENOUGH WITH THEIR ENUNCIATION AND NEARLY CAUSED ANOTHER PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: UNCLR CTLR PHRASEOLOGY AND THE PIECES OF INFO THAT THE FLC HAD AVAILABLE; ALL CORRELATED TO MAKE UP A CLRNC THAT WAS EXPECTED. WHAT THE DC9-30 CREW DIDN'T EXPECT WAS THAT THERE WAS ANOTHER FLT HOLDING SHORT WITH A VERY SIMILAR NAME AND THE SAME FLT NUMBER. SUPPLEMENTAL INFO FROM ACN 350923: IT SHOULD BE NOTED THAT THE CTLR'S PRONUNCIATION OF OUR AIRLINE AND THEIR AIRLINE SOUNDED ALIKE. I DON'T KNOW IF THE FLT NUMBERS MAY HAVE CAUSED MOMENTARY CONFUSION ON HIS PART; BUT THE CAPT AND I BOTH HEARD OUR CALL SIGN; I READ BACK HIS CLRNC VERBATIM; AND WE EXECUTED HIS ORDERS. AS AN ASIDE; I HAVE MADE IT A PERSONAL POLICY TO READ BACK ALL INSTRUCTIONS VERBATIM WHEN TAXIING ONTO; OR XING AN ACTIVE RWY; DUE TO AN ACCIDENT THERE; BECAUSE OF A RWY INCURSION SEVERAL YRS AGO. FURTHER; AS I UNDERSTAND IT; MARKETING DEPTS SET UP THESE FLT NUMBERS; AND THE PRACTICE OF HAVING SAME NUMBER FLTS AT THE SAME ARPT ONLY SERVE TO CONFUSE ATC AND FLCS; WHEN BOTH ARE BUSY. AS YOU ARE WELL AWARE; REAL WORLD OPS; WITH TFC; CHKLISTS; RADIO COMS; AND MANEUVERING OF THE ACFT -- USING SIMILAR NUMBERS AT AN ARPT -- ONLY SERVES TO SET EVERYONE UP.