Narrative:

We were given a clearance to 'descend to cross ATR at 16000'', then maintain 14000'. Due to the manner in which the controller issued the clearance, both the captain and I interpreted the clearance as 'cross ATR at 16000, maintain 14000'.' about 4 mi north of the VOR we passed 15000' and the controller clarified his clearance, stressing the word 'then'. No conflict existed and the controller told us not to worry about it. Both the captain and I were surprised that we both could have missed the 'then' portion of the clearance, but perhaps we became a bit too complacent with this regular route into washington, dc. In the future we'll not only verify our clearance, but our readbacks as well. Thanks for your time.

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Original NASA ASRS Text

Title: ACR MLG ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative: WE WERE GIVEN A CLRNC TO 'DSND TO CROSS ATR AT 16000'', THEN MAINTAIN 14000'. DUE TO THE MANNER IN WHICH THE CTLR ISSUED THE CLRNC, BOTH THE CAPT AND I INTERPRETED THE CLRNC AS 'CROSS ATR AT 16000, MAINTAIN 14000'.' ABOUT 4 MI N OF THE VOR WE PASSED 15000' AND THE CTLR CLARIFIED HIS CLRNC, STRESSING THE WORD 'THEN'. NO CONFLICT EXISTED AND THE CTLR TOLD US NOT TO WORRY ABOUT IT. BOTH THE CAPT AND I WERE SURPRISED THAT WE BOTH COULD HAVE MISSED THE 'THEN' PORTION OF THE CLRNC, BUT PERHAPS WE BECAME A BIT TOO COMPLACENT WITH THIS REGULAR ROUTE INTO WASHINGTON, DC. IN THE FUTURE WE'LL NOT ONLY VERIFY OUR CLRNC, BUT OUR READBACKS AS WELL. THANKS FOR YOUR TIME.

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