Narrative:

During descent, cleared direct bur down to 9000 ft. I inadvertently descended to 8000 ft before ATC said, 'I show you low, continue descent to 8000 ft.' we were tired after a long day and I apparently misunderstood clearance and thought we were cleared to 8000 ft. I was correcting when reclred to 8000 ft.

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Original NASA ASRS Text

Title: THE PF MISUNDERSTOOD CLRNC ALT. FLC DISCOVERED DEV AND INITIATED CORRECTION WHEN ATC INTERVENED. PLT CLAIMED FATIGUE RELATED. CHARTER OP.

Narrative: DURING DSCNT, CLRED DIRECT BUR DOWN TO 9000 FT. I INADVERTENTLY DSNDED TO 8000 FT BEFORE ATC SAID, 'I SHOW YOU LOW, CONTINUE DSCNT TO 8000 FT.' WE WERE TIRED AFTER A LONG DAY AND I APPARENTLY MISUNDERSTOOD CLRNC AND THOUGHT WE WERE CLRED TO 8000 FT. I WAS CORRECTING WHEN RECLRED TO 8000 FT.

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.