Narrative:

Our aircraft was not involved. We observed the incident from the intersection of txwys B and D. 5 mins prior to incursion, I heard ground control (at sfo) clear a 'Y' aircraft under tow to 'cross runway 28L, hold short of runway 28R.' the mechanic fumbled the readback the first time, but got it correct the second time. By the time we got to the above-mentioned intersection, the aircraft under tow was just beginning to cross runway 28L. I don't know why he delayed so long. We looked up to see a plane (another air carrier Z -- don't know who it was because we were not listening to the local position) on short final. We could not tell if he was lined up for runway 28R or runway 28L (nighttime). The aircraft under tow stopped in the middle of runway 28L (crossing at taxiway east) just as the other aircraft touched down on runway 28L. The landing aircraft Z stopped short, and there was no collision. My opinion: the local controller gave permission to the ground controller to let the aircraft under tow cross runway 28L, but he took so long to do it that the local controller forgot about it and cleared someone else to land. There were no combined ATC position, and the WX was clear VFR. I don't know who is responsible here, but the incident needs to be documented. We've got to stop these runway incursions.

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Original NASA ASRS Text

Title: ACFT UNDER TOW OCCUPIES RWY AT SFO, CA, WHILE ANOTHER ACR ACFT LANDS ON THE SAME RWY.

Narrative: OUR ACFT WAS NOT INVOLVED. WE OBSERVED THE INCIDENT FROM THE INTXN OF TXWYS B AND D. 5 MINS PRIOR TO INCURSION, I HEARD GND CTL (AT SFO) CLR A 'Y' ACFT UNDER TOW TO 'CROSS RWY 28L, HOLD SHORT OF RWY 28R.' THE MECH FUMBLED THE READBACK THE FIRST TIME, BUT GOT IT CORRECT THE SECOND TIME. BY THE TIME WE GOT TO THE ABOVE-MENTIONED INTXN, THE ACFT UNDER TOW WAS JUST BEGINNING TO CROSS RWY 28L. I DON'T KNOW WHY HE DELAYED SO LONG. WE LOOKED UP TO SEE A PLANE (ANOTHER ACR Z -- DON'T KNOW WHO IT WAS BECAUSE WE WERE NOT LISTENING TO THE LCL POS) ON SHORT FINAL. WE COULD NOT TELL IF HE WAS LINED UP FOR RWY 28R OR RWY 28L (NIGHTTIME). THE ACFT UNDER TOW STOPPED IN THE MIDDLE OF RWY 28L (XING AT TXWY E) JUST AS THE OTHER ACFT TOUCHED DOWN ON RWY 28L. THE LNDG ACFT Z STOPPED SHORT, AND THERE WAS NO COLLISION. MY OPINION: THE LCL CTLR GAVE PERMISSION TO THE GND CTLR TO LET THE ACFT UNDER TOW CROSS RWY 28L, BUT HE TOOK SO LONG TO DO IT THAT THE LCL CTLR FORGOT ABOUT IT AND CLRED SOMEONE ELSE TO LAND. THERE WERE NO COMBINED ATC POS, AND THE WX WAS CLR VFR. I DON'T KNOW WHO IS RESPONSIBLE HERE, BUT THE INCIDENT NEEDS TO BE DOCUMENTED. WE'VE GOT TO STOP THESE RWY INCURSIONS.

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.