Narrative:

Air carrier X was issued descent to FL300. Controller meant to say FL350. Supplemental information from acn 781243: during cruise at FL360; ARTCC issued clearance to FL300. Descending through FL340; ARTCC said our assigned altitude was FL350. I was informed via radio that a pilot deviation had occurred. A review of the audio tape showed that the clearance had indeed been to descend to FL300.

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Original NASA ASRS Text

Title: ZID CTLR EXPERIENCED OPDEV WHEN ISSUING WRONG ALT AND THEN FAILING TO HEAR READBACK.

Narrative: ACR X WAS ISSUED DSCNT TO FL300. CTLR MEANT TO SAY FL350. SUPPLEMENTAL INFO FROM ACN 781243: DURING CRUISE AT FL360; ARTCC ISSUED CLRNC TO FL300. DSNDING THROUGH FL340; ARTCC SAID OUR ASSIGNED ALT WAS FL350. I WAS INFORMED VIA RADIO THAT A PLTDEV HAD OCCURRED. A REVIEW OF THE AUDIO TAPE SHOWED THAT THE CLRNC HAD INDEED BEEN TO DSND TO FL300.

Data retrieved from NASA's ASRS site as of May 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.