ACR ACFT WITH SIMILAR SOUNDING CALL SIGN TAKES WRONG TKOF CLRNC AND CONFLICTS WITH 2 ACFT XING THE RWY. CTLR DID NOT CATCH WRONG READBACK.

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AFTER AN UNEVENTFUL TAXI TO RWY 22R; GND CTL SENT US TO TWR FREQ (123.9). A B767 WAS CLRED FOR TKOF; WHICH LEFT US #1 FOR THE ACTIVE RWY. TWR CALLED 'ACR X; CLRED INTO POS AND HOLD RWY 22R.' I ANSWERED; 'ACR X ON TO HOLD RWY 22R.' I BEGAN THE BEFORE TKOF CHKLIST. PRIOR TO COMPLETING THE CHKLIST AND PRIOR TO PULLING ON THE RWY; TWR CALLED 'ACR X CLRED FOR TKOF.' I REPEATED THE CLRNC 'ACR X; CLRED FOR TKOF.' THE CAPT (THE PF) AND I COMPLETED THE BEFORE TKOF CHKLIST AS HE LINED UP ON THE RWY AND PUSHED UP THE PWR. THE CAPT'S FOCUS WAS OUTSIDE THE COCKPIT FOR RWY ALIGNMENT; WHILE I WAS CONCENTRATED INSIDE THE COCKPIT; CHKING ENG INSTS AND MAKING OUR STANDARD CALLOUTS. AFTER CALLING OUT '80 KTS; ENG INSTS CHKED;' I BEGAN TO FOCUS SOME OF MY ATTN TO OUTSIDE THE COCKPIT. AT APPROX 90-100 KTS THE CAPT SAID SOMETHING AND; IN AN INSTANT; JERKED THE THROTTLES BACK A SMALL AMOUNT AND THEN RESET THEM TO TKOF PWR. THIS HAPPENED IN A SPLIT SECOND. I REALIZED HE HAD CONSIDERED ABORTING THE TKOF; BUT HAD THEN DECIDED TO CONTINUE. AT FIRST I DIDN'T KNOW WHY; BUT AN INSTANT LATER I COULD SEE FARTHER DOWN THE RWY THAT AN ACFT HAD BEEN XING THE RWY AND WAS JUST CLRING IT AT THIS TIME. I BELIEVE THE CAPT DECIDED TO CONTINUE BECAUSE THE AIRPLANE WAS CLRING THE RWY AND IT WAS SAFER TO CONTINUE; RATHER THAN PERFORM A HIGH SPD ABORT. AS WE PASSED THE TXWY WHERE THE ACFT HAD CROSSED THE RWY; IT APPEARED THAT ANOTHER ACFT HAD ALSO JUST CROSSED THE RWY ON ANOTHER TXWY FURTHER DOWN RWY 22R FROM THE FIRST ACFT. WE ROTATED; CLBED OUT; AND CONTINUED OUR FLT IN A NORMAL FASHION. THERE HAD BEEN A RWY CHANGE IN PROGRESS; PREVIOUS TO OUR DEP. THE CAPT DID AN OUTSTANDING JOB DETERMINING THE SAFEST COURSE OF ACTION FOR US TO TAKE IN THIS SIT; AS THE XING ACFT WAS JUST CLRING THE RWY AND THERE WAS A LOT OF DISTANCE BTWN US. SUPPLEMENTAL INFO FROM ACN 325193: AS WE WERE CLRED INTO POS THE TWR ASSIGNED US A CLBOUT HDG OF 200 DEGS; AND STATED THAT THERE WAS TFC ON A 6 MI FINAL. AS I STARTED THE R TURN TO ALIGN THE ACFT TO THE RWY CTRLINE; I HEARD THE SAME VOICE THAT HAD CLRED US INTO POS CLR US FOR TKOF. THE COPLT RESPONDED 'ROGER; ACR X CLRED FOR TKOF.' I CALLED FOR THE COMPLETION OF THE BEFORE TKOF CHKLIST AND COMMENCED THE TKOF ROLL. AT ABOUT 80 KTS AN ACFT CAME INTO VIEW THAT WAS XING THE RWY L TO R; WITH ABOUT 1/3 OF THE FUSELAGE STILL OVER THE RWY. I COULD SEE THAT THE XING ACFT WAS ACCELERATING OFF THE RWY AND WOULD BE WELL CLR AS I PASSED IT; BUT I SHADED OUR ACFT TO THE L OF CTRLINE IN CASE THE OTHER ACFT STOPPED FOR SOME REASON. AS WE PASSED THE XING ACFT; A SECOND AIRPLANE CAME INTO VIEW; ALSO XING THE RWY FROM L TO R; BUT ONE TXWY FURTHER DOWN THE RWY. THIS ACFT WAS ALSO ACCELERATING CLR. WE ROTATED ABOUT OPPOSITE THE SECOND ACFT AND THE REST OF THE DEP WAS NORMAL. AT ABOUT 400 FT I CONFIRMED WITH THE COPLT THAT WE HAD BEEN CLRED FOR TKOF; BECAUSE SOMEONE HAD OBVIOUSLY MADE A MISTAKE. I TOLD HIM WE WOULD HAVE AN INDICATION OF WHO HAD ERRED; IF THE TWR TURNED US OVER TO DEP CTL NORMALLY. AT 1500 FT KENNEDY TWR CALLED (WITH A LOT OF CHATTER IN THE BACKGND) AND SAID; 'ACR X CONTACT DEP ON 135.9.' NEWSPAPER ACCOUNTS HAVE STATED THAT THE FAA HAS ACCEPTED RESPONSIBILITY BECAUSE THEY DID NOT ADVISE US THAT THERE WAS AN ACR Y (SAME NUMBER) ON THE FREQ. SUPPLEMENTAL INFO FROM ACN 325179: I WAS WORKING THE DEP LCL CTL POS; 2 RWYS -- RWY 22R AND RWY 31L. ARR CTLR WORKING RWY 22L. HOLDING IN POS ON RWY 22R; ACR X; MD80; HOLDING IN POS FROM INTXN KK N SIDE OF RWY 22R. ACR Y (SAME NUMBERS) B767. I ADVISED THE ARR LCL CTLR TO CROSS 2 ACFT ACROSS RWY 22R. I CLRED ACR Y FOR TKOF. WHEN I OBSERVED HIM NOT ROLLING I ASKED IF HE COPIED THE CLRNC. HE SAID HE HEARD IT BUT ACR X ACKNOWLEDGED IT. I LOOKED TO MY L AND SAW ACR X ON TKOF ROLL AT LEAST 1/3 DOWN THE RWY NEAR ROTATION; ALSO OBSERVED AN ACR Z XING RWY 22R AHEAD. ACR X ROTATED WHILE ACR Z WAS CLRING. ACR X MADE NO COMMENTS. ACR Z UPON REACHING THE GATE CALLED THE TWR. CONTRIBUTING FACTORS: PERFORMING MOST OF MY OWN COORD WITHOUT A CAB COORDINATOR. ACR X AND ACR Y -- I WAS NOT AWARE; WENT THROUGH THE SYS WITHOUT BEING POINTED OUT. I DID NOT HEAR ACR X READBACK; BUT IT WAS ON TAPE. I SPECIFIED THE RWY; HE DID NOT.