Narrative:

Level at 12000 ft. ATC asked for altitude and we advised level at 12000 ft. ATC stated our clearance was only 16000 ft. Altitude alert was set to 12000 ft, we thought and advised ATC that we were cleared to 12000 ft. ATC advised no problem and for us to maintain 12000 ft. The captain and myself are both very conscientious with altitude awareness procedures, so this was an obvious surprise to both of us. The captain was getting ATIS about the time of the clearance and he doesn't remember getting the clearance, and I don't remember anything out of the ordinary. Controller stated that he might have missed the readback.

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Original NASA ASRS Text

Title: B737-300 MAINTAINING 12000 FT NE OF MANTA INTXN, CTLR ADVISED ONLY CLRED TO 16000 FT. ALT ALERT HAD BEEN SET TO 12000 FT. ZNY ADVISED NO PROB, MAINTAIN 12000 FT.

Narrative: LEVEL AT 12000 FT. ATC ASKED FOR ALT AND WE ADVISED LEVEL AT 12000 FT. ATC STATED OUR CLRNC WAS ONLY 16000 FT. ALT ALERT WAS SET TO 12000 FT, WE THOUGHT AND ADVISED ATC THAT WE WERE CLRED TO 12000 FT. ATC ADVISED NO PROB AND FOR US TO MAINTAIN 12000 FT. THE CAPT AND MYSELF ARE BOTH VERY CONSCIENTIOUS WITH ALT AWARENESS PROCS, SO THIS WAS AN OBVIOUS SURPRISE TO BOTH OF US. THE CAPT WAS GETTING ATIS ABOUT THE TIME OF THE CLRNC AND HE DOESN'T REMEMBER GETTING THE CLRNC, AND I DON'T REMEMBER ANYTHING OUT OF THE ORDINARY. CTLR STATED THAT HE MIGHT HAVE MISSED THE READBACK.

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.