Narrative:

We were told to take the next high speed taxiway off of 25L and hold short of 25R as there was traffic in our alleyway blocking our passage to the gate. We were holding short when I thought I heard our callsign. Looked across at the captain, his hand was already moving the throttles forward which seemed like confirmation or our clearance now to cross 25R without delay which I repeated back, including our callsign. We shot across the runway looking in both directions down the runway but could see no traffic on final, which seemed odd! After crossing we noticed that some fire trucks had been called out. It occurred to me at that point that they probably needed the taxiway that we occupied while holding short of 25R. The ground controller now told us to turn right and double back on the inner taxiway and told us to contact the tower when we blocked in, which we did. The tower chief asked us why we crossed the runway without a clearance. Apparently the clearance was for another aircraft. No deviations or go arounds or dangerous situations developed because of our crossing. We asked why our readback remained uncorrected as we were still approximately 75' from the runway after acknowledging their transmission. Apparently we were blocked. I should have challenged the ctrl as I wasn't totally sure of the tower's callsign. Seeing the throttles move by the captain made me think, well it must have been us. We were the only ones waiting to cross after all. This particular airport has 2 parallel runways on the north side as well however. As a commuter, I had been awake for approximately 19 hours and felt exhausted. My questioning ability was not up to PAR as it usually is. We were rescheduled earlier in the day because of bad WX at an earlier airport. This current airport was not even in our intinerary. The tower chief did comment on how quickly we crossed the runway. A case of mistaken identity perhaps. Supplemental information from acn 153506. The first officer said that my hand moving to the throttles as he readback the clearance was a confirmation for him that I'd heard the clearance as he heard it. I told him that wasn't my intent. At this point, both of us had already confirmed that there was traffic about a mile out on final and that the runway was clear. I later spoke with the tower supervisor to determine what his intentions were. He'd apparently discussed the situation with the involved local controller and had decided that we'd taken a crossing clearance for another aircraft, that our crossing presented no safety or control problems and that readbacks from both the aircraft actually cleared to cross and from us occurred exactly simultaneously and that our readback was blocked by the other aircraft.

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Original NASA ASRS Text

Title: CROSSED ACTIVE RWY WITHOUT CLRNC.

Narrative: WE WERE TOLD TO TAKE THE NEXT HIGH SPD TXWY OFF OF 25L AND HOLD SHORT OF 25R AS THERE WAS TFC IN OUR ALLEYWAY BLOCKING OUR PASSAGE TO THE GATE. WE WERE HOLDING SHORT WHEN I THOUGHT I HEARD OUR CALLSIGN. LOOKED ACROSS AT THE CAPT, HIS HAND WAS ALREADY MOVING THE THROTTLES FORWARD WHICH SEEMED LIKE CONFIRMATION OR OUR CLRNC NOW TO CROSS 25R WITHOUT DELAY WHICH I REPEATED BACK, INCLUDING OUR CALLSIGN. WE SHOT ACROSS THE RWY LOOKING IN BOTH DIRECTIONS DOWN THE RWY BUT COULD SEE NO TFC ON FINAL, WHICH SEEMED ODD! AFTER XING WE NOTICED THAT SOME FIRE TRUCKS HAD BEEN CALLED OUT. IT OCCURRED TO ME AT THAT POINT THAT THEY PROBABLY NEEDED THE TXWY THAT WE OCCUPIED WHILE HOLDING SHORT OF 25R. THE GND CTLR NOW TOLD US TO TURN RIGHT AND DOUBLE BACK ON THE INNER TXWY AND TOLD US TO CONTACT THE TWR WHEN WE BLOCKED IN, WHICH WE DID. THE TWR CHIEF ASKED US WHY WE CROSSED THE RWY WITHOUT A CLRNC. APPARENTLY THE CLRNC WAS FOR ANOTHER ACFT. NO DEVIATIONS OR GO AROUNDS OR DANGEROUS SITUATIONS DEVELOPED BECAUSE OF OUR XING. WE ASKED WHY OUR READBACK REMAINED UNCORRECTED AS WE WERE STILL APPROX 75' FROM THE RWY AFTER ACKNOWLEDGING THEIR XMISSION. APPARENTLY WE WERE BLOCKED. I SHOULD HAVE CHALLENGED THE CTRL AS I WASN'T TOTALLY SURE OF THE TWR'S CALLSIGN. SEEING THE THROTTLES MOVE BY THE CAPT MADE ME THINK, WELL IT MUST HAVE BEEN US. WE WERE THE ONLY ONES WAITING TO CROSS AFTER ALL. THIS PARTICULAR ARPT HAS 2 PARALLEL RWYS ON THE NORTH SIDE AS WELL HOWEVER. AS A COMMUTER, I HAD BEEN AWAKE FOR APPROX 19 HRS AND FELT EXHAUSTED. MY QUESTIONING ABILITY WAS NOT UP TO PAR AS IT USUALLY IS. WE WERE RESCHEDULED EARLIER IN THE DAY BECAUSE OF BAD WX AT AN EARLIER ARPT. THIS CURRENT ARPT WAS NOT EVEN IN OUR INTINERARY. THE TWR CHIEF DID COMMENT ON HOW QUICKLY WE CROSSED THE RWY. A CASE OF MISTAKEN IDENTITY PERHAPS. SUPPLEMENTAL INFORMATION FROM ACN 153506. THE F/O SAID THAT MY HAND MOVING TO THE THROTTLES AS HE READBACK THE CLRNC WAS A CONFIRMATION FOR HIM THAT I'D HEARD THE CLRNC AS HE HEARD IT. I TOLD HIM THAT WASN'T MY INTENT. AT THIS POINT, BOTH OF US HAD ALREADY CONFIRMED THAT THERE WAS TFC ABOUT A MILE OUT ON FINAL AND THAT THE RWY WAS CLR. I LATER SPOKE WITH THE TWR SUPVR TO DETERMINE WHAT HIS INTENTIONS WERE. HE'D APPARENTLY DISCUSSED THE SITUATION WITH THE INVOLVED LCL CTLR AND HAD DECIDED THAT WE'D TAKEN A XING CLRNC FOR ANOTHER ACFT, THAT OUR XING PRESENTED NO SAFETY OR CTL PROBS AND THAT READBACKS FROM BOTH THE ACFT ACTUALLY CLRED TO CROSS AND FROM US OCCURRED EXACTLY SIMULTANEOUSLY AND THAT OUR READBACK WAS BLOCKED BY THE OTHER ACFT.

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.