Air carrier flight crew answers clearance intended for another air carrier.

Attributes
ACN	434700
Time
Date	199904
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : mod.vor
State Reference	CA
Altitude	msl bound lower : 33000 msl bound upper : 35000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa.artcc
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Route In Use	arrival star : mod.2
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zoa.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Route In Use	arrival star : mod.2
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	434700
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	non adherence : clearance non adherence : far
Independent Detector	atc equipment other atc equipment : radar other controllera
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Read back altitude change FL350 for FL310 to oak. Left frequency to get ATIS. Returned to see first officer passing through FL330 and asked by ATC why we were descending. We had answered for air carrier 20 mi ahead of us. No altitude separation loss. ATC said no report. Numerous vectors and speed changes during arrival along with altitude and frequency changes. ATC was not confirming any readbacks.

Original NASA ASRS Text

Title: ACR FLC ANSWERS CLRNC INTENDED FOR ANOTHER ACR.

Narrative: READ BACK ALT CHANGE FL350 FOR FL310 TO OAK. LEFT FREQ TO GET ATIS. RETURNED TO SEE FO PASSING THROUGH FL330 AND ASKED BY ATC WHY WE WERE DSNDING. WE HAD ANSWERED FOR ACR 20 MI AHEAD OF US. NO ALT SEPARATION LOSS. ATC SAID NO RPT. NUMEROUS VECTORS AND SPD CHANGES DURING ARR ALONG WITH ALT AND FREQ CHANGES. ATC WAS NOT CONFIRMING ANY READBACKS.

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.