Narrative:

We were assigned to descend from FL350 to FL270. At about FL280, first officer turned on the seatbelt sign and began his appropriate PA. At about FL275, I heard ZDV clear us to cross quail at 17000 ft and read it back. When done transmitting, I heard another aircraft also reading it back. Then denver said the clearance was for air carrier Y. I had already entered 17000 ft in altitude window and was through FL270 during the correction. We leveled at FL266 and denver then cleared us to quail at 17000 ft. We had started slow climb back to FL270, got as high as FL277, then started the descent again. No traffic conflicts were noted on our TCASII during this time. Factors: one person hearing the clearance -- I was sure I heard our call sign, but noticed that we had been flying with air carrier Y's call sign earlier. It's possible I reacted to it in error. Supplemental information from acn 606827: the combination of expecting the descent clearance, hearing it given to a familiar flight number, and one person off the frequency at precisely the wrong time, led to this altitude deviation. Although the controller may have alleviated the deviation with a timely clearance, it still occurred. Sometimes there is a need for an immediate reset of the alerter to maintain a tight descent profile. However, if there's no rush, a confirmation per SOP's certainly is appropriate. Although there was no technical violation of SOP, the captain could have waited a few seconds for the altitude capture and allowed me to confirm the lower altitude when I came back on frequency.

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Original NASA ASRS Text

Title: B737 DSNDING INTO DEN WITH ZDV RESPONDED TO CLRNC FOR ANOTHER ACFT.

Narrative: WE WERE ASSIGNED TO DSND FROM FL350 TO FL270. AT ABOUT FL280, FO TURNED ON THE SEATBELT SIGN AND BEGAN HIS APPROPRIATE PA. AT ABOUT FL275, I HEARD ZDV CLR US TO CROSS QUAIL AT 17000 FT AND READ IT BACK. WHEN DONE XMITTING, I HEARD ANOTHER ACFT ALSO READING IT BACK. THEN DENVER SAID THE CLRNC WAS FOR ACR Y. I HAD ALREADY ENTERED 17000 FT IN ALT WINDOW AND WAS THROUGH FL270 DURING THE CORRECTION. WE LEVELED AT FL266 AND DENVER THEN CLRED US TO QUAIL AT 17000 FT. WE HAD STARTED SLOW CLB BACK TO FL270, GOT AS HIGH AS FL277, THEN STARTED THE DSCNT AGAIN. NO TFC CONFLICTS WERE NOTED ON OUR TCASII DURING THIS TIME. FACTORS: ONE PERSON HEARING THE CLRNC -- I WAS SURE I HEARD OUR CALL SIGN, BUT NOTICED THAT WE HAD BEEN FLYING WITH ACR Y'S CALL SIGN EARLIER. IT'S POSSIBLE I REACTED TO IT IN ERROR. SUPPLEMENTAL INFO FROM ACN 606827: THE COMBINATION OF EXPECTING THE DSCNT CLRNC, HEARING IT GIVEN TO A FAMILIAR FLT NUMBER, AND ONE PERSON OFF THE FREQ AT PRECISELY THE WRONG TIME, LED TO THIS ALTDEV. ALTHOUGH THE CTLR MAY HAVE ALLEVIATED THE DEV WITH A TIMELY CLRNC, IT STILL OCCURRED. SOMETIMES THERE IS A NEED FOR AN IMMEDIATE RESET OF THE ALERTER TO MAINTAIN A TIGHT DSCNT PROFILE. HOWEVER, IF THERE'S NO RUSH, A CONFIRMATION PER SOP'S CERTAINLY IS APPROPRIATE. ALTHOUGH THERE WAS NO TECHNICAL VIOLATION OF SOP, THE CAPT COULD HAVE WAITED A FEW SECONDS FOR THE ALT CAPTURE AND ALLOWED ME TO CONFIRM THE LOWER ALT WHEN I CAME BACK ON FREQ.

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.