Narrative:

We were on air carrier flight xa mexico city to dfw. We were flying the acton 9 STAR to dfw. We had descended to 19000' at an assigned airspeed of 320 KIAS. Our position was over acton and we were expecting to cross a fix (flato, 22 NM northeast of acton) at 11000' and 250 KIAS. We had already passed the point for a normal descent. We were being held up due to traffic below and ahead of us at 17000'. At this point the copilot and I heard ZFW clear us (air carrier xa) to 11000'. The copilot acknowledged, 'roger, cleared to 11000.' I started a descent through 18500' when I heard (air carrier xb) transmit to ZFW that someone else had taken their clearance to 11000'. At this point, I leveled the aircraft at 18300' and directed the copilot to confirm our clearance. ZFW indicated that we were supposed to be at 19000' although we were clear of traffic and were now clearance to cross (flato) at 11000'. We were not aware that air carrier xb was on our frequency. Therefore, when air carrier xb radioed that someone else had taken their descent clearance, this was the first time we were aware of a similar call sign. The frequency was quite busy and apparently we had taken air carrier xb clearance, although we were certain in our minds it was for us and acknowledged the clearance. I think 2 corrective actions could help prevent a recurrence: 1) change flight #'south of aircraft with similar flight #'south, arriving at an airport at the same time. 2) although I know the controller was very busy, advising us of a similar call sigh would help also. Normally the controllers at ZFW do tell us of similar flight #'south, time permitting.

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Original NASA ASRS Text

Title: CONFUSION CAUSED BY SIMILAR CALL SIGNS OF THE SAME ACR ON THE SAME FREQ CAUSED THE REPORTER ACFT TO ACCEPT THE DESCENT CLRNC OF ANOTHER ACFT AND TO BEGIN DESCENT FROM CLEARED ALT.

Narrative: WE WERE ON ACR FLT XA MEXICO CITY TO DFW. WE WERE FLYING THE ACTON 9 STAR TO DFW. WE HAD DSNDED TO 19000' AT AN ASSIGNED AIRSPD OF 320 KIAS. OUR POS WAS OVER ACTON AND WE WERE EXPECTING TO CROSS A FIX (FLATO, 22 NM NE OF ACTON) AT 11000' AND 250 KIAS. WE HAD ALREADY PASSED THE POINT FOR A NORMAL DSCNT. WE WERE BEING HELD UP DUE TO TFC BELOW AND AHEAD OF US AT 17000'. AT THIS POINT THE COPLT AND I HEARD ZFW CLR US (ACR XA) TO 11000'. THE COPLT ACKNOWLEDGED, 'ROGER, CLRED TO 11000.' I STARTED A DSCNT THROUGH 18500' WHEN I HEARD (ACR XB) XMIT TO ZFW THAT SOMEONE ELSE HAD TAKEN THEIR CLRNC TO 11000'. AT THIS POINT, I LEVELED THE ACFT AT 18300' AND DIRECTED THE COPLT TO CONFIRM OUR CLRNC. ZFW INDICATED THAT WE WERE SUPPOSED TO BE AT 19000' ALTHOUGH WE WERE CLR OF TFC AND WERE NOW CLRNC TO CROSS (FLATO) AT 11000'. WE WERE NOT AWARE THAT ACR XB WAS ON OUR FREQ. THEREFORE, WHEN ACR XB RADIOED THAT SOMEONE ELSE HAD TAKEN THEIR DSCNT CLRNC, THIS WAS THE FIRST TIME WE WERE AWARE OF A SIMILAR CALL SIGN. THE FREQ WAS QUITE BUSY AND APPARENTLY WE HAD TAKEN ACR XB CLRNC, ALTHOUGH WE WERE CERTAIN IN OUR MINDS IT WAS FOR US AND ACKNOWLEDGED THE CLRNC. I THINK 2 CORRECTIVE ACTIONS COULD HELP PREVENT A RECURRENCE: 1) CHANGE FLT #'S OF ACFT WITH SIMILAR FLT #'S, ARRIVING AT AN ARPT AT THE SAME TIME. 2) ALTHOUGH I KNOW THE CTLR WAS VERY BUSY, ADVISING US OF A SIMILAR CALL SIGH WOULD HELP ALSO. NORMALLY THE CTLRS AT ZFW DO TELL US OF SIMILAR FLT #'S, TIME PERMITTING.

Data retrieved from NASA's ASRS site as of August 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.