Narrative:

On descent we were given an altitude of 10000' for level off. At the same time, I, (first officer) was asking the captain to request a turn further to the left and a further descent to clear buildups (observed) visually and on our radar. When den approach asked our altitude we replied 'ten thousand' at the same time checking that 10000' was in the altitude alert window. At this point there was a discussion in the cockpit. The captain saying he had originally repeated 11000' and thought he had put 11000' in the window. I said I thought I had heard 10000' from the controller. Just about this time the controller said 'no conflict, continue the descent to 8000''. During this whole time the FAA jumpseat rider said nothing, even though he had been listening on the headset. It's possible that the captain had actually set 11000' in the window and I could have hit the altitude knob while trying to maneuver the aircraft in the turbulence with the heading knob, mistakenly knocking the altitude knob from 11000' to 10000'. After parking the aircraft the FAA maintenance inspector said we had done a good job but that I had definitely heard wrong and that it had been 10000' (it would have helped if he would have said something about it at the time).

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR MLG FLT CREW CONFUSED IF CLEARD TO 10000' OR 11000' ON DESCENT TO DEN.

Narrative: ON DSNT WE WERE GIVEN AN ALT OF 10000' FOR LEVEL OFF. AT THE SAME TIME, I, (F/O) WAS ASKING THE CAPT TO REQUEST A TURN FURTHER TO THE L AND A FURTHER DSNT TO CLR BUILDUPS (OBSERVED) VISUALLY AND ON OUR RADAR. WHEN DEN APCH ASKED OUR ALT WE REPLIED 'TEN THOUSAND' AT THE SAME TIME CHKING THAT 10000' WAS IN THE ALT ALERT WINDOW. AT THIS POINT THERE WAS A DISCUSSION IN THE COCKPIT. THE CAPT SAYING HE HAD ORIGINALLY REPEATED 11000' AND THOUGHT HE HAD PUT 11000' IN THE WINDOW. I SAID I THOUGHT I HAD HEARD 10000' FROM THE CTLR. JUST ABOUT THIS TIME THE CTLR SAID 'NO CONFLICT, CONTINUE THE DSNT TO 8000''. DURING THIS WHOLE TIME THE FAA JUMPSEAT RIDER SAID NOTHING, EVEN THOUGH HE HAD BEEN LISTENING ON THE HEADSET. IT'S POSSIBLE THAT THE CAPT HAD ACTUALLY SET 11000' IN THE WINDOW AND I COULD HAVE HIT THE ALT KNOB WHILE TRYING TO MANEUVER THE ACFT IN THE TURB WITH THE HDG KNOB, MISTAKENLY KNOCKING THE ALT KNOB FROM 11000' TO 10000'. AFTER PARKING THE ACFT THE FAA MAINT INSPECTOR SAID WE HAD DONE A GOOD JOB BUT THAT I HAD DEFINITELY HEARD WRONG AND THAT IT HAD BEEN 10000' (IT WOULD HAVE HELPED IF HE WOULD HAVE SAID SOMETHING ABOUT IT AT THE TIME).

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.