Narrative:

Holding short of runway 1R on taxiway M awaiting clearance to cross for departure on runway 7. Aircraft was facing approximately 240 degrees on taxiway M. I heard a clearance to cross the runway and acknowledged same. The captain taxied across the runway on my word that we had been cleared. While crossing, I looked down the runway and at first saw nothing because of the heat waves rising. After a moment or two, and while on the runway, I saw an aircraft rolling towards us. The aircraft was displaying no lights and I assumed that it had landed and was rolling out. We sat short of runway 7 for 5-7 mins awaiting departure clearance and nothing was said about conflicting traffic to us by the tower. We were cleared onto the runway and the tower remarked, casually, that we had crossed west/O clearance. I replied that ground control had cleared us and I had acknowledged same. Possibly, I misunderstood ground control. But, nothing was said while we were crossing the runway or for the period while we were waiting departure clearance. Callback conversation with reporter revealed the following: reporter says he thought he heard air carrier a xyz cleared to cross 19L and answered with the full call sign and repeated clearance. Apparently an small aircraft somewhere of airport possibly cleared to cross runway 19R and reporter says he may have heard as clearance for him. Did not know call sign of small aircraft. Tape playback revealed that all of widebody transport readback expect runway 19L was stepped on apparently by the small aircraft answering. Angle widebody transport was holding precluded them from seeing back up the runway until they had turned to cross runway 19L. FAA is investigating the incident and has threatened the PIC with penalty. Supplemental information from acn 91320: while I was reviewing the departure plate I thought I heard, 'clearance to cross.' when I looked at the copilot he was in the process of stating, 'roger xyz, cleared to cross.' as we started across I looked down runway 19. We observed an aircraft headed towards us, although at the far end. Since it was displaying no lights and decelerating, we assumed he had landed and was clearing. We were waiting for takeoff clearance approximately 7 mins west/O any comments from the tower, whose frequency we had shifted to after crossing runway 19. Then, almost as an aside as we were given clearance to takeoff, the tower operator stated, 'you forced abc to abort when you crossed runway 19L.' it is possible the copilot misunderstood ground control's instructions, but when he acknowledged the clearance no one corrected him. We cannot understand why someone didn't immediately contact us and attempt to determine what went wrong.

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Original NASA ASRS Text

Title: ACR WDB RESPONDED TO WRONG CLRNC AND CROSSED ACTIVE WITHOUT CAUSING ACR B TO ABORT TKOF.

Narrative: HOLDING SHORT OF RWY 1R ON TXWY M AWAITING CLRNC TO CROSS FOR DEP ON RWY 7. ACFT WAS FACING APPROX 240 DEGS ON TXWY M. I HEARD A CLRNC TO CROSS THE RWY AND ACKNOWLEDGED SAME. THE CAPT TAXIED ACROSS THE RWY ON MY WORD THAT WE HAD BEEN CLRED. WHILE XING, I LOOKED DOWN THE RWY AND AT FIRST SAW NOTHING BECAUSE OF THE HEAT WAVES RISING. AFTER A MOMENT OR TWO, AND WHILE ON THE RWY, I SAW AN ACFT ROLLING TOWARDS US. THE ACFT WAS DISPLAYING NO LIGHTS AND I ASSUMED THAT IT HAD LANDED AND WAS ROLLING OUT. WE SAT SHORT OF RWY 7 FOR 5-7 MINS AWAITING DEP CLRNC AND NOTHING WAS SAID ABOUT CONFLICTING TFC TO US BY THE TWR. WE WERE CLRED ONTO THE RWY AND THE TWR REMARKED, CASUALLY, THAT WE HAD CROSSED W/O CLRNC. I REPLIED THAT GND CTL HAD CLRED US AND I HAD ACKNOWLEDGED SAME. POSSIBLY, I MISUNDERSTOOD GND CTL. BUT, NOTHING WAS SAID WHILE WE WERE XING THE RWY OR FOR THE PERIOD WHILE WE WERE WAITING DEP CLRNC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR SAYS HE THOUGHT HE HEARD ACR A XYZ CLRED TO CROSS 19L AND ANSWERED WITH THE FULL CALL SIGN AND REPEATED CLRNC. APPARENTLY AN SMA SOMEWHERE OF ARPT POSSIBLY CLRED TO CROSS RWY 19R AND RPTR SAYS HE MAY HAVE HEARD AS CLRNC FOR HIM. DID NOT KNOW CALL SIGN OF SMA. TAPE PLAYBACK REVEALED THAT ALL OF WDB READBACK EXPECT RWY 19L WAS STEPPED ON APPARENTLY BY THE SMA ANSWERING. ANGLE WDB WAS HOLDING PRECLUDED THEM FROM SEEING BACK UP THE RWY UNTIL THEY HAD TURNED TO CROSS RWY 19L. FAA IS INVESTIGATING THE INCIDENT AND HAS THREATENED THE PIC WITH PENALTY. SUPPLEMENTAL INFO FROM ACN 91320: WHILE I WAS REVIEWING THE DEP PLATE I THOUGHT I HEARD, 'CLRNC TO CROSS.' WHEN I LOOKED AT THE COPLT HE WAS IN THE PROCESS OF STATING, 'ROGER XYZ, CLRED TO CROSS.' AS WE STARTED ACROSS I LOOKED DOWN RWY 19. WE OBSERVED AN ACFT HEADED TOWARDS US, ALTHOUGH AT THE FAR END. SINCE IT WAS DISPLAYING NO LIGHTS AND DECELERATING, WE ASSUMED HE HAD LANDED AND WAS CLRING. WE WERE WAITING FOR TKOF CLRNC APPROX 7 MINS W/O ANY COMMENTS FROM THE TWR, WHOSE FREQ WE HAD SHIFTED TO AFTER XING RWY 19. THEN, ALMOST AS AN ASIDE AS WE WERE GIVEN CLRNC TO TKOF, THE TWR OPERATOR STATED, 'YOU FORCED ABC TO ABORT WHEN YOU CROSSED RWY 19L.' IT IS POSSIBLE THE COPLT MISUNDERSTOOD GND CTL'S INSTRUCTIONS, BUT WHEN HE ACKNOWLEDGED THE CLRNC NO ONE CORRECTED HIM. WE CANNOT UNDERSTAND WHY SOMEONE DIDN'T IMMEDIATELY CONTACT US AND ATTEMPT TO DETERMINE WHAT WENT WRONG.

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.