Narrative:

E145 was issued clearance 'amend altitude; climb and maintain FL290.' pilot clipped initial word but replied '...(clipped) to FL290?' with a questioning tone as to the altitude. I re-stated 'affirmative FL290.' pilot replied '290.' pilot continued to climb through FL290 to FL330 which was the original clearance level. Upon hearing playback of tape; it appears pilot may have said 'expedite to FL290.' my clearance was textbook without question 'amend altitude.' I questioned the pilot to verify he was level at FL290 even though mode C indicated FL293. He said negative; his clearance was to expedite to FL290. Expedite was not part of any clearance of his or any other aircraft on the frequency at that time. His readback indicated he was climbing to FL290; not through FL290. There was a subsequent phone call between the pilot and our omic. The pilot stated he saw the traffic at FL300 and leveled off at FL290; then resumed climb after passing traffic. Traffic in the sector was complex. There were flow control initiatives adding to complexity and automation problems at the time of the error. Error was discovered through conflict alert oedp. I believe my clearance was clear and left no room for question or doubt. ZAU in yrs past had a local supplement to the 7110.65 requiring controllers to receive a 'complete readback.' this supplement was allowed to expire and was removed a long time ago. Maybe it would be beneficial to reinstate this policy.

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Original NASA ASRS Text

Title: ZAU CTLR EXPERIENCED OPERROR AT FL300 WHEN READBACK FROM PLT WAS ABSENT AND OR INCORRECT.

Narrative: E145 WAS ISSUED CLRNC 'AMEND ALT; CLB AND MAINTAIN FL290.' PLT CLIPPED INITIAL WORD BUT REPLIED '...(CLIPPED) TO FL290?' WITH A QUESTIONING TONE AS TO THE ALT. I RE-STATED 'AFFIRMATIVE FL290.' PLT REPLIED '290.' PLT CONTINUED TO CLB THROUGH FL290 TO FL330 WHICH WAS THE ORIGINAL CLRNC LEVEL. UPON HEARING PLAYBACK OF TAPE; IT APPEARS PLT MAY HAVE SAID 'EXPEDITE TO FL290.' MY CLRNC WAS TEXTBOOK WITHOUT QUESTION 'AMEND ALT.' I QUESTIONED THE PLT TO VERIFY HE WAS LEVEL AT FL290 EVEN THOUGH MODE C INDICATED FL293. HE SAID NEGATIVE; HIS CLRNC WAS TO EXPEDITE TO FL290. EXPEDITE WAS NOT PART OF ANY CLRNC OF HIS OR ANY OTHER ACFT ON THE FREQ AT THAT TIME. HIS READBACK INDICATED HE WAS CLBING TO FL290; NOT THROUGH FL290. THERE WAS A SUBSEQUENT PHONE CALL BTWN THE PLT AND OUR OMIC. THE PLT STATED HE SAW THE TFC AT FL300 AND LEVELED OFF AT FL290; THEN RESUMED CLB AFTER PASSING TFC. TFC IN THE SECTOR WAS COMPLEX. THERE WERE FLOW CTL INITIATIVES ADDING TO COMPLEXITY AND AUTOMATION PROBS AT THE TIME OF THE ERROR. ERROR WAS DISCOVERED THROUGH CONFLICT ALERT OEDP. I BELIEVE MY CLRNC WAS CLR AND LEFT NO ROOM FOR QUESTION OR DOUBT. ZAU IN YRS PAST HAD A LCL SUPPLEMENT TO THE 7110.65 REQUIRING CTLRS TO RECEIVE A 'COMPLETE READBACK.' THIS SUPPLEMENT WAS ALLOWED TO EXPIRE AND WAS REMOVED A LONG TIME AGO. MAYBE IT WOULD BE BENEFICIAL TO REINSTATE THIS POLICY.

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