Narrative:

First officer (aircraft X) received clearance to descend to FL310 from FL390 and read back clearance. At FL380 controller stated we should have remained at FL390, climb back to FL390. I was involved with a medical emergency with first flight attendant and never heard the communications. Notably, aircraft Y was on the frequency. I spoke to the controller's supervisor by telephone 1 hour later, and she did not hear the conversation(south) between the first officer and controller. We agreed that aircraft Y may have caused the confusion. No action is planned legally, tapes are being pulled and supervisor and myself will discuss later. Apparently, the controller had 2 sits while we had the medical emergency, all with similar flight numbers X and Y. No evasive action was required and no conflicts existed per the supervisor.

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Original NASA ASRS Text

Title: FLC ACCEPTED A CLRNC FOR ANOTHER ACFT AND DEPARTED ASSIGNED ALT.

Narrative: FO (ACFT X) RECEIVED CLRNC TO DSND TO FL310 FROM FL390 AND READ BACK CLRNC. AT FL380 CTLR STATED WE SHOULD HAVE REMAINED AT FL390, CLB BACK TO FL390. I WAS INVOLVED WITH A MEDICAL EMER WITH FIRST FLT ATTENDANT AND NEVER HEARD THE COMS. NOTABLY, ACFT Y WAS ON THE FREQ. I SPOKE TO THE CTLR'S SUPVR BY TELEPHONE 1 HR LATER, AND SHE DID NOT HEAR THE CONVERSATION(S) BTWN THE FO AND CTLR. WE AGREED THAT ACFT Y MAY HAVE CAUSED THE CONFUSION. NO ACTION IS PLANNED LEGALLY, TAPES ARE BEING PULLED AND SUPVR AND MYSELF WILL DISCUSS LATER. APPARENTLY, THE CTLR HAD 2 SITS WHILE WE HAD THE MEDICAL EMER, ALL WITH SIMILAR FLT NUMBERS X AND Y. NO EVASIVE ACTION WAS REQUIRED AND NO CONFLICTS EXISTED PER THE SUPVR.

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.