Narrative:

Appeared to be #1 for takeoff runway 32R ord. Heard air carrier X no delay clear for takeoff runway 32R heading 040 degrees. I read back clearance as stated and noted an air carrier Y jet on the roll runway 32R. When in position tower asked what we were doing. We replied we were cleared for takeoff. Tower advised us to hold position and soon after cleared us for takeoff. After takeoff we heard air carrier Y and realized that we may have responded to his takeoff clearance and blocked his response. I did not hear any other aircraft respond when I did. The final for runway 32R was clear and we had sight of the aircraft landing runway 27R.

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Original NASA ASRS Text

Title: B737 TAXIING FOR DEP AT ORD ENTERS RWY WITHOUT ATC CLRNC.

Narrative: APPEARED TO BE #1 FOR TKOF RWY 32R ORD. HEARD ACR X NO DELAY CLR FOR TKOF RWY 32R HEADING 040 DEGS. I READ BACK CLRNC AS STATED AND NOTED AN ACR Y JET ON THE ROLL RWY 32R. WHEN IN POS TWR ASKED WHAT WE WERE DOING. WE REPLIED WE WERE CLRED FOR TKOF. TWR ADVISED US TO HOLD POS AND SOON AFTER CLRED US FOR TKOF. AFTER TKOF WE HEARD ACR Y AND REALIZED THAT WE MAY HAVE RESPONDED TO HIS TKOF CLRNC AND BLOCKED HIS RESPONSE. I DID NOT HEAR ANY OTHER ACFT RESPOND WHEN I DID. THE FINAL FOR RWY 32R WAS CLR AND WE HAD SIGHT OF THE ACFT LNDG RWY 27R.

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.