Narrative:

While talking to ont tower prior to takeoff there was confusion between our aircraft and an small transport Y with a very similar call sign. We were cleared to cross 8L and hold short of 8R at taxiway 20. While holding short the tower say 'air carrier X, cleared for takeoff.' I responded 'air carrier X cleared for takeoff on 8R.' there was no correction by the tower until we were almost lined up with runway heading, at which time I heard the tower say 'air carrier X cancel takeoff clearance.' since we were already on the runway, I said 'roger air carrier X is position and hold, cancelling clearance.' at that time I noticed the small transport Y half way down the runway facing toward us. The tower then said 'you are not cleared position and hold.' at this point it became confusing whether tower was talking to us or the small transport Y as I heard the other aircraft responding to calls I believed were meant for us. As we started to maneuver off the runway, the small transport Y taxied clear of the runway, and tower cleared us for takeoff on 8R. I could not differentiate any difference in 'call signs' from tower xmissions between our aircraft and that of the other aircraft. Apparently the tower had trouble telling the difference as well since immediate corrections did not follow our xmissions and response to tower calls. I was not aware of the existence of the other aircraft until we took the runway in preparation for takeoff.

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Original NASA ASRS Text

Title: ACFT CLRED FOR TKOF, WRONG ACFT DOWNFIELD STARTS TKOF ROLL. PLTDEV.

Narrative: WHILE TALKING TO ONT TWR PRIOR TO TKOF THERE WAS CONFUSION BTWN OUR ACFT AND AN SMT Y WITH A VERY SIMILAR CALL SIGN. WE WERE CLRED TO CROSS 8L AND HOLD SHORT OF 8R AT TAXIWAY 20. WHILE HOLDING SHORT THE TWR SAY 'ACR X, CLRED FOR TKOF.' I RESPONDED 'ACR X CLRED FOR TKOF ON 8R.' THERE WAS NO CORRECTION BY THE TWR UNTIL WE WERE ALMOST LINED UP WITH RWY HDG, AT WHICH TIME I HEARD THE TWR SAY 'ACR X CANCEL TKOF CLRNC.' SINCE WE WERE ALREADY ON THE RWY, I SAID 'ROGER ACR X IS POS AND HOLD, CANCELLING CLRNC.' AT THAT TIME I NOTICED THE SMT Y HALF WAY DOWN THE RWY FACING TOWARD US. THE TWR THEN SAID 'YOU ARE NOT CLRED POS AND HOLD.' AT THIS POINT IT BECAME CONFUSING WHETHER TWR WAS TALKING TO US OR THE SMT Y AS I HEARD THE OTHER ACFT RESPONDING TO CALLS I BELIEVED WERE MEANT FOR US. AS WE STARTED TO MANEUVER OFF THE RWY, THE SMT Y TAXIED CLR OF THE RWY, AND TWR CLRED US FOR TKOF ON 8R. I COULD NOT DIFFERENTIATE ANY DIFFERENCE IN 'CALL SIGNS' FROM TWR XMISSIONS BTWN OUR ACFT AND THAT OF THE OTHER ACFT. APPARENTLY THE TWR HAD TROUBLE TELLING THE DIFFERENCE AS WELL SINCE IMMEDIATE CORRECTIONS DID NOT FOLLOW OUR XMISSIONS AND RESPONSE TO TWR CALLS. I WAS NOT AWARE OF THE EXISTENCE OF THE OTHER ACFT UNTIL WE TOOK THE RWY IN PREPARATION FOR TKOF.

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.