Narrative:

Outbnd from boi we were cleared to FL230. At the above noted time airline flight Y was inbound to boi. Requested 17000' and center advised as an inappropriate altitude for direction. Flight Y then requested something VFR. Then Y called center as X requesting 16000'. Center approved X to 16000'. As we (the actual X) were passing through 16000' we tried to break into center and advise him airline flight Y had in fact requested 16000', but were unable to do so before Y had begun his descent and caused center a conflict. Center advised Y and an unknown small aircraft Z to take evasive action. Center then called us (X) to confirm our altitude and we advised we were cleared to FL230. Conflict was between airline fly Y and small aircraft Z. The problem was caused by airline flight Y calling himself airline flight X, and himself apparently confused as to what he really wanted for an altitude. Additionally there was apparently a lack of crew coordination on flight Y as the PF did not catch the PNF's mistake and began a descent on a clearance for airline flight X. I question myself as to whether I should have stopped my climb at 16000' knowing the clearance was given to airline flight X in error, and I in fact should be good to FL230. The center controller was noticeably shaken by this event and apologized for making a mistake. He did not and should know it.

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Original NASA ASRS Text

Title: LOSS OF SEPARATION OCCURS AS ARTCC RADAR CTLR GETS CONFUSED BY ACR USING WRONG CALL SIGN AND ISSUES DESCENT CLRNC TO ACFT WHO CALLED WITH WRONG CALL SIGN. THE REAL FLT WITH THAT MISUSED CALL SIGN WAS, COINCIDENTALLY, JUST CLIMBING THROUGH THE ALT THAT THE OTHER ACFT HAD REQUESTED. THE ACFT WHO USED WRONG CALL SIGN ALSO RESPONDED TO THAT CALL SIGN AND WAS VECTORED AWAY FROM AN SMA.

Narrative: OUTBND FROM BOI WE WERE CLRED TO FL230. AT THE ABOVE NOTED TIME AIRLINE FLT Y WAS INBND TO BOI. REQUESTED 17000' AND CENTER ADVISED AS AN INAPPROPRIATE ALT FOR DIRECTION. FLT Y THEN REQUESTED SOMETHING VFR. THEN Y CALLED CENTER AS X REQUESTING 16000'. CENTER APPROVED X TO 16000'. AS WE (THE ACTUAL X) WERE PASSING THROUGH 16000' WE TRIED TO BREAK INTO CENTER AND ADVISE HIM AIRLINE FLT Y HAD IN FACT REQUESTED 16000', BUT WERE UNABLE TO DO SO BEFORE Y HAD BEGUN HIS DSCNT AND CAUSED CENTER A CONFLICT. CENTER ADVISED Y AND AN UNKNOWN SMA Z TO TAKE EVASIVE ACTION. CENTER THEN CALLED US (X) TO CONFIRM OUR ALT AND WE ADVISED WE WERE CLRED TO FL230. CONFLICT WAS BTWN AIRLINE FLY Y AND SMA Z. THE PROB WAS CAUSED BY AIRLINE FLT Y CALLING HIMSELF AIRLINE FLT X, AND HIMSELF APPARENTLY CONFUSED AS TO WHAT HE REALLY WANTED FOR AN ALT. ADDITIONALLY THERE WAS APPARENTLY A LACK OF CREW COORD ON FLT Y AS THE PF DID NOT CATCH THE PNF'S MISTAKE AND BEGAN A DSCNT ON A CLRNC FOR AIRLINE FLT X. I QUESTION MYSELF AS TO WHETHER I SHOULD HAVE STOPPED MY CLB AT 16000' KNOWING THE CLRNC WAS GIVEN TO AIRLINE FLT X IN ERROR, AND I IN FACT SHOULD BE GOOD TO FL230. THE CENTER CTLR WAS NOTICEABLY SHAKEN BY THIS EVENT AND APOLOGIZED FOR MAKING A MISTAKE. HE DID NOT AND SHOULD KNOW IT.

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.