Narrative:

At approximately XA00, while plting air carrier X airbus from seattle to los angeles, we were given a descent by ZOA to descend from FL330 to FL240. We read back 'roger, aircraft X descending to FL240.' several mins later, ZOA called us and inquired, 'aircraft X, what's your assigned altitude?' we responded 'center, you cleared aircraft X to FL240, and that's what we read back.' ZOA then directed us (aircraft X) to maintain FL290. Moments later, we heard another aircraft with a similar call sign (aircraft Y) check in with ZOA. I then realized that the controller was talking to both of us, but he never told us about the other air carrier aircraft with a similar call sign. It appeared that the controller got confused when we (aircraft X) acknowledged the descent. There was no known midair conflict on TCASII. What could have prevented this confusion problem would be for the controller to announce to both aircraft Y and aircraft X that similar call signs were on the same frequency. This would have prompted both air crews to increase situational awareness for potential conflict ahead of aircraft.

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Original NASA ASRS Text

Title: ACR ACKNOWLEDGES ZOA ALT CLRNC CHANGE, ONLY A FEW MINS LATER TO BE CHALLENGED BY THE CTLR. WITHIN MOMENTS, A COMPANY ACR CHKS ON FREQ WITH A SIMILAR CALL SIGN.

Narrative: AT APPROX XA00, WHILE PLTING ACR X AIRBUS FROM SEATTLE TO LOS ANGELES, WE WERE GIVEN A DSCNT BY ZOA TO DSND FROM FL330 TO FL240. WE READ BACK 'ROGER, ACFT X DSNDING TO FL240.' SEVERAL MINS LATER, ZOA CALLED US AND INQUIRED, 'ACFT X, WHAT'S YOUR ASSIGNED ALT?' WE RESPONDED 'CTR, YOU CLRED ACFT X TO FL240, AND THAT'S WHAT WE READ BACK.' ZOA THEN DIRECTED US (ACFT X) TO MAINTAIN FL290. MOMENTS LATER, WE HEARD ANOTHER ACFT WITH A SIMILAR CALL SIGN (ACFT Y) CHK IN WITH ZOA. I THEN REALIZED THAT THE CTLR WAS TALKING TO BOTH OF US, BUT HE NEVER TOLD US ABOUT THE OTHER ACR ACFT WITH A SIMILAR CALL SIGN. IT APPEARED THAT THE CTLR GOT CONFUSED WHEN WE (ACFT X) ACKNOWLEDGED THE DSCNT. THERE WAS NO KNOWN MIDAIR CONFLICT ON TCASII. WHAT COULD HAVE PREVENTED THIS CONFUSION PROB WOULD BE FOR THE CTLR TO ANNOUNCE TO BOTH ACFT Y AND ACFT X THAT SIMILAR CALL SIGNS WERE ON THE SAME FREQ. THIS WOULD HAVE PROMPTED BOTH AIR CREWS TO INCREASE SITUATIONAL AWARENESS FOR POTENTIAL CONFLICT AHEAD OF ACFT.

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.