Narrative:

Air carrier X was coming out of the gulf of mexico nebound. Air carrier Y was sebound towards pie. Both were at FL370. I had air carrier Y on a 180 degree heading to go behind another aircraft at FL370 on the same flight path as air carrier X. I then cleared air carrier Y back on course toward pie. I realized that air carrier X and air carrier Y were going to be in conflict, so I turned air carrier X to a 070 degree heading and air carrier Y back to a 190 degree heading. I asked air carrier Y to expedite his turn to the 190 degree heading. I then turned the air carrier X to a 090 degree heading because it didn't look like he was flying a 070 degree heading. I also descended the air carrier X to FL350. Air carrier Y read back the clearance to descend to FL350, but I didn't catch that it was air carrier Y reading it back. I then called traffic to air carrier Y and told him that air carrier X was descending to FL350. A few seconds later, I noticed the mode C on air carrier Y and asked if he was responding to TCASII or something. He said no, that he was descending to FL350. This put air carrier Y in conflict with another aircraft coming out of the gulf that I had taken from FL370 to FL350 to miss air carrier Y. I then had to expedite air carrier Y on down to FL330. After ensuring that air carrier Y was level at FL330, I put him back on course. There were many contributing factors to this situation. Pilots need to be more attentive during the cruise stage of flight and have more responsibility for when they take clrncs that were delivered to other aircraft. Air carrier X had a very strong accent and it was very hard to understand his readbacks. There was lots of backgnd noise caused by shout lines to ZMA and the need for lots of coordination during heavy traffic.

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Original NASA ASRS Text

Title: ZJX CTLR DID NOT NOTICE A READBACK FROM THE WRONG ACFT RESULTING IN A LOSS OF SEPARATION.

Narrative: ACR X WAS COMING OUT OF THE GULF OF MEXICO NEBOUND. ACR Y WAS SEBOUND TOWARDS PIE. BOTH WERE AT FL370. I HAD ACR Y ON A 180 DEG HDG TO GO BEHIND ANOTHER ACFT AT FL370 ON THE SAME FLT PATH AS ACR X. I THEN CLRED ACR Y BACK ON COURSE TOWARD PIE. I REALIZED THAT ACR X AND ACR Y WERE GOING TO BE IN CONFLICT, SO I TURNED ACR X TO A 070 DEG HDG AND ACR Y BACK TO A 190 DEG HDG. I ASKED ACR Y TO EXPEDITE HIS TURN TO THE 190 DEG HDG. I THEN TURNED THE ACR X TO A 090 DEG HDG BECAUSE IT DIDN'T LOOK LIKE HE WAS FLYING A 070 DEG HDG. I ALSO DSNDED THE ACR X TO FL350. ACR Y READ BACK THE CLRNC TO DSND TO FL350, BUT I DIDN'T CATCH THAT IT WAS ACR Y READING IT BACK. I THEN CALLED TFC TO ACR Y AND TOLD HIM THAT ACR X WAS DSNDING TO FL350. A FEW SECONDS LATER, I NOTICED THE MODE C ON ACR Y AND ASKED IF HE WAS RESPONDING TO TCASII OR SOMETHING. HE SAID NO, THAT HE WAS DSNDING TO FL350. THIS PUT ACR Y IN CONFLICT WITH ANOTHER ACFT COMING OUT OF THE GULF THAT I HAD TAKEN FROM FL370 TO FL350 TO MISS ACR Y. I THEN HAD TO EXPEDITE ACR Y ON DOWN TO FL330. AFTER ENSURING THAT ACR Y WAS LEVEL AT FL330, I PUT HIM BACK ON COURSE. THERE WERE MANY CONTRIBUTING FACTORS TO THIS SIT. PLTS NEED TO BE MORE ATTENTIVE DURING THE CRUISE STAGE OF FLT AND HAVE MORE RESPONSIBILITY FOR WHEN THEY TAKE CLRNCS THAT WERE DELIVERED TO OTHER ACFT. ACR X HAD A VERY STRONG ACCENT AND IT WAS VERY HARD TO UNDERSTAND HIS READBACKS. THERE WAS LOTS OF BACKGND NOISE CAUSED BY SHOUT LINES TO ZMA AND THE NEED FOR LOTS OF COORD DURING HVY TFC.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.