Narrative:

While controling air carrier Y bcb (#2) by hec VOR; air carrier X bcb checked in (#1). Neither myself nor assistant realized the similar call sign. Air carrier Y was issued descent to FL250 from FL280. The readback was out of FL380 for FL250 bcb. No company in the call sign. Later air carrier Y questioned the clearance. Air carrier X was observed leaving FL375 descending and was told to maintain FL360. After listening to the recording 80% of aircraft readbacks were just numbers with no company. We were lucky this time. This is a system-wide problem that needs to be addressed.

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Original NASA ASRS Text

Title: ZLA CTLR DESCRIBED SIMILAR CALL SIGN INCIDENT THAT RESULTED IN THE WRONG ACFT STARTING A DSCNT.

Narrative: WHILE CTLING ACR Y BCB (#2) BY HEC VOR; ACR X BCB CHKED IN (#1). NEITHER MYSELF NOR ASSISTANT REALIZED THE SIMILAR CALL SIGN. ACR Y WAS ISSUED DSCNT TO FL250 FROM FL280. THE READBACK WAS OUT OF FL380 FOR FL250 BCB. NO COMPANY IN THE CALL SIGN. LATER ACR Y QUESTIONED THE CLRNC. ACR X WAS OBSERVED LEAVING FL375 DSNDING AND WAS TOLD TO MAINTAIN FL360. AFTER LISTENING TO THE RECORDING 80% OF ACFT READBACKS WERE JUST NUMBERS WITH NO COMPANY. WE WERE LUCKY THIS TIME. THIS IS A SYS-WIDE PROB THAT NEEDS TO BE ADDRESSED.

Data retrieved from NASA's ASRS site as of January 2009 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.