Narrative:

We were en route from bur to sjc, established on the roble 2 arrival north of the avenal VOR crossing at FL350. ZLA gave a clearance for pilot's discretion descent to FL240. The captain and I both heard our flight number. It was read back and we both acknowledged it as the new altitude was selected in the MCP. Approximately 5-6 mins later, I began the descent to FL240. At FL345 ATC said 'verify you are at FL350.' the captain replied 'we have started down to FL240.' ATC replied 'negative, that clearance was for someone else, climb and maintain FL350.' while descending at approximately FL345 we also received an RA from our TCASII. It was opposite direction traffic at FL330 (an MD80). (I had already begun my climb back to FL350 at this time. We did not go any lower than FL342 during our recovery.) we had visual contact with the traffic as it passed 1 - 1 1/2 mi to our left at FL330. When we checked on frequency, we were never cautioned for a similar sounding call sign in use. Had ATC advised us of this information, it would have helped us considerably. Once on the ground in san jose we called ZLA by phone. While talking with the ATC supervisor he told us that company flight had advised his next ATC controller that they thought someone else had acknowledged their descent clearance to FL240. We were never advised or cautioned, and there was never any questions from ATC as to whether we or anyone else had unknowingly taken the wrong clearance. I believe that had ATC cautioned us of the similar call sign, this deviation would have been avoided.

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Original NASA ASRS Text

Title: FLC RESPONDED TO ANOTHER ACFT'S DSCNT CLRNC.

Narrative: WE WERE ENRTE FROM BUR TO SJC, ESTABLISHED ON THE ROBLE 2 ARR N OF THE AVENAL VOR XING AT FL350. ZLA GAVE A CLRNC FOR PLT'S DISCRETION DSCNT TO FL240. THE CAPT AND I BOTH HEARD OUR FLT NUMBER. IT WAS READ BACK AND WE BOTH ACKNOWLEDGED IT AS THE NEW ALT WAS SELECTED IN THE MCP. APPROX 5-6 MINS LATER, I BEGAN THE DSCNT TO FL240. AT FL345 ATC SAID 'VERIFY YOU ARE AT FL350.' THE CAPT REPLIED 'WE HAVE STARTED DOWN TO FL240.' ATC REPLIED 'NEGATIVE, THAT CLRNC WAS FOR SOMEONE ELSE, CLB AND MAINTAIN FL350.' WHILE DSNDING AT APPROX FL345 WE ALSO RECEIVED AN RA FROM OUR TCASII. IT WAS OPPOSITE DIRECTION TFC AT FL330 (AN MD80). (I HAD ALREADY BEGUN MY CLB BACK TO FL350 AT THIS TIME. WE DID NOT GO ANY LOWER THAN FL342 DURING OUR RECOVERY.) WE HAD VISUAL CONTACT WITH THE TFC AS IT PASSED 1 - 1 1/2 MI TO OUR L AT FL330. WHEN WE CHKED ON FREQ, WE WERE NEVER CAUTIONED FOR A SIMILAR SOUNDING CALL SIGN IN USE. HAD ATC ADVISED US OF THIS INFO, IT WOULD HAVE HELPED US CONSIDERABLY. ONCE ON THE GND IN SAN JOSE WE CALLED ZLA BY PHONE. WHILE TALKING WITH THE ATC SUPVR HE TOLD US THAT COMPANY FLT HAD ADVISED HIS NEXT ATC CTLR THAT THEY THOUGHT SOMEONE ELSE HAD ACKNOWLEDGED THEIR DSCNT CLRNC TO FL240. WE WERE NEVER ADVISED OR CAUTIONED, AND THERE WAS NEVER ANY QUESTIONS FROM ATC AS TO WHETHER WE OR ANYONE ELSE HAD UNKNOWINGLY TAKEN THE WRONG CLRNC. I BELIEVE THAT HAD ATC CAUTIONED US OF THE SIMILAR CALL SIGN, THIS DEV WOULD HAVE BEEN AVOIDED.

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.