Narrative:

Route lax to phx, between thermal and blythe VOR, climbing through FL315 to 330. Several aircraft deviating south of normal route around thunderstorms. ZLA cleared us to FL330, our normal cruising altitude. FL330 was set in altitude alert and first officer repeated, 'cleared to 330,' as per company operating procedure. Climbing through FL315, controller asked, 'medium large transport X, say altitude.' I replied, 'climbing through 31.5 for 330.' controller immediately said, 'descend down to FL290.' we complied and when he gave us a frequency change, I asked if there was a problem. He said there was no problem. On the ground at phx, I called ZLA to inquire about the altitude change and was told that during a controller change we were inadvertently cleared to FL330 by previous controller and that no report would be filed on the altitude deviation.

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Original NASA ASRS Text

Title: ACR MLG CLIMBED TO THE WRONG ALT DURING WX DEVIATIONS AND DISCOVERED BY THE RELIEVING CTLR AND CORRECTED.

Narrative: ROUTE LAX TO PHX, BTWN THERMAL AND BLYTHE VOR, CLBING THROUGH FL315 TO 330. SEVERAL ACFT DEVIATING S OF NORMAL ROUTE AROUND TSTMS. ZLA CLRED US TO FL330, OUR NORMAL CRUISING ALT. FL330 WAS SET IN ALT ALERT AND F/O REPEATED, 'CLRED TO 330,' AS PER COMPANY OPERATING PROC. CLBING THROUGH FL315, CTLR ASKED, 'MLG X, SAY ALT.' I REPLIED, 'CLBING THROUGH 31.5 FOR 330.' CTLR IMMEDIATELY SAID, 'DSND DOWN TO FL290.' WE COMPLIED AND WHEN HE GAVE US A FREQ CHANGE, I ASKED IF THERE WAS A PROB. HE SAID THERE WAS NO PROB. ON THE GND AT PHX, I CALLED ZLA TO INQUIRE ABOUT THE ALT CHANGE AND WAS TOLD THAT DURING A CTLR CHANGE WE WERE INADVERTENTLY CLRED TO FL330 BY PREVIOUS CTLR AND THAT NO RPT WOULD BE FILED ON THE ALT DEVIATION.

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.