Narrative:

We were 10 NM west of crean; inbound to sfo at FL380. Air carrier Y was approximately 5 NM ahead of us; at FL390. We had both been given a squawk. Air carrier Y had been called in radar contact a couple of mins earlier. We were both talking to ZOA. The ride began to get choppy and both air carrier Y and ourselves asked for lower altitude. We were both very close to top of descent position. Oak heard both our requests and responded; 'air carrier Y descend and maintain FL350.' he read back the clearance. Our position was approximately 5 NM behind him; and 2 NM offset to the right of his track to crean. When the controller saw air carrier Y in a descent he asked; 'air carrier Y say cleared altitude.' air carrier Y responded with FL350. The controller gave us a 30 degree right turn and instructed air carrier Y to maintain altitude. We turned and told the controller that we concurred with air carrier Y that the descent clearance was for him; not us; and he had read it back. I believe the controller momentarily got confused with both of us asking for lower; and gave the descent clearance to air carrier Y instead of us. Neither of us asked him to acknowledge the mistake; but I'm quite sure that is what happened. No TCAS alert went off; and we were VFR and in sight of air carrier Y.

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Original NASA ASRS Text

Title: B777; SFO ARR; AT FL380 EXPERIENCED CONFLICT WITH PRECEDING TFC AT FL390 WHEN ATC ERRED AND ISSUED DESCENT TO FL390 ACFT; OPERROR RECORDED.

Narrative: WE WERE 10 NM W OF CREAN; INBOUND TO SFO AT FL380. ACR Y WAS APPROX 5 NM AHEAD OF US; AT FL390. WE HAD BOTH BEEN GIVEN A SQUAWK. ACR Y HAD BEEN CALLED IN RADAR CONTACT A COUPLE OF MINS EARLIER. WE WERE BOTH TALKING TO ZOA. THE RIDE BEGAN TO GET CHOPPY AND BOTH ACR Y AND OURSELVES ASKED FOR LOWER ALT. WE WERE BOTH VERY CLOSE TO TOP OF DSCNT POS. OAK HEARD BOTH OUR REQUESTS AND RESPONDED; 'ACR Y DSND AND MAINTAIN FL350.' HE READ BACK THE CLRNC. OUR POS WAS APPROX 5 NM BEHIND HIM; AND 2 NM OFFSET TO THE R OF HIS TRACK TO CREAN. WHEN THE CTLR SAW ACR Y IN A DSCNT HE ASKED; 'ACR Y SAY CLRED ALT.' ACR Y RESPONDED WITH FL350. THE CTLR GAVE US A 30 DEG R TURN AND INSTRUCTED ACR Y TO MAINTAIN ALT. WE TURNED AND TOLD THE CTLR THAT WE CONCURRED WITH ACR Y THAT THE DSCNT CLRNC WAS FOR HIM; NOT US; AND HE HAD READ IT BACK. I BELIEVE THE CTLR MOMENTARILY GOT CONFUSED WITH BOTH OF US ASKING FOR LOWER; AND GAVE THE DSCNT CLRNC TO ACR Y INSTEAD OF US. NEITHER OF US ASKED HIM TO ACKNOWLEDGE THE MISTAKE; BUT I'M QUITE SURE THAT IS WHAT HAPPENED. NO TCAS ALERT WENT OFF; AND WE WERE VFR AND IN SIGHT OF ACR Y.

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.