Narrative:

ZID climbing out cleared to FL350 and read back FL350. At 32500' ZID asked our altitude. Told them FL325. They said we were only cleared to FL310, and they must have missed the readback. We descended to FL310.

Google
 

Original NASA ASRS Text

Title: ALT BUST.

Narrative: ZID CLBING OUT CLRED TO FL350 AND READ BACK FL350. AT 32500' ZID ASKED OUR ALT. TOLD THEM FL325. THEY SAID WE WERE ONLY CLRED TO FL310, AND THEY MUST HAVE MISSED THE READBACK. WE DSNDED TO FL310.

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.