Narrative:

With an FAA airworthiness inspector in the jump seat, we crossed a hold short line on taxiway B which placed the nose of the aircraft across an extended runway edge line for runway 5L. Were not handed off to tower, so we requested handoff to tower. When we were initially cleared to taxi, we were told to follow an aircraft ahead of us. We were cleared to runway 5L, the other aircraft was cleared to runway 5R. Since we had earlier discussed the possibility of using runway 5R, I got in my 'follow the leader' mode and continued to follow the other aircraft. After we had crossed the hold short line for runway 5L, the FAA inspector asked if we had been cleared to cross runway 5L and we immediately held our position, told tower of our whereabouts and were cleared to continue our taxi to runway 5R. Factors contributing to our mistake were: darkness, poorly lit (if lit at all), poor placement of runway signs, first officer heads down in cockpit, and captain's poor situational awareness. Runway 5L was not in use at the time. Supplemental information from acn 562486: 2/3 of the way to the runway, I (the first officer) spilled a cup of water on my approach plates. My attention was taken away from critical duties of clearing as I was cleaning up the mess. I also asked the captain if he would like runway 5R for takeoff. He reviewed the airport diagram and decided not to request runway 5R. The captain later confided that he thought we were cleared to follow the aircraft. That aircraft was cleared by tower to taxi to runway 5R.

Google
 

Original NASA ASRS Text

Title: RWY INCURSION AFTER AN S80 FLC IS DISTR WITH DUTIES AND CLRNC REGARDING RWY ASSIGNMENT DURING A NIGHT OP AT MMMX, FO.

Narrative: WITH AN FAA AIRWORTHINESS INSPECTOR IN THE JUMP SEAT, WE CROSSED A HOLD SHORT LINE ON TXWY B WHICH PLACED THE NOSE OF THE ACFT ACROSS AN EXTENDED RWY EDGE LINE FOR RWY 5L. WERE NOT HANDED OFF TO TWR, SO WE REQUESTED HDOF TO TWR. WHEN WE WERE INITIALLY CLRED TO TAXI, WE WERE TOLD TO FOLLOW AN ACFT AHEAD OF US. WE WERE CLRED TO RWY 5L, THE OTHER ACFT WAS CLRED TO RWY 5R. SINCE WE HAD EARLIER DISCUSSED THE POSSIBILITY OF USING RWY 5R, I GOT IN MY 'FOLLOW THE LEADER' MODE AND CONTINUED TO FOLLOW THE OTHER ACFT. AFTER WE HAD CROSSED THE HOLD SHORT LINE FOR RWY 5L, THE FAA INSPECTOR ASKED IF WE HAD BEEN CLRED TO CROSS RWY 5L AND WE IMMEDIATELY HELD OUR POS, TOLD TWR OF OUR WHEREABOUTS AND WERE CLRED TO CONTINUE OUR TAXI TO RWY 5R. FACTORS CONTRIBUTING TO OUR MISTAKE WERE: DARKNESS, POORLY LIT (IF LIT AT ALL), POOR PLACEMENT OF RWY SIGNS, FO HEADS DOWN IN COCKPIT, AND CAPT'S POOR SITUATIONAL AWARENESS. RWY 5L WAS NOT IN USE AT THE TIME. SUPPLEMENTAL INFO FROM ACN 562486: 2/3 OF THE WAY TO THE RWY, I (THE FO) SPILLED A CUP OF WATER ON MY APCH PLATES. MY ATTN WAS TAKEN AWAY FROM CRITICAL DUTIES OF CLRING AS I WAS CLEANING UP THE MESS. I ALSO ASKED THE CAPT IF HE WOULD LIKE RWY 5R FOR TKOF. HE REVIEWED THE ARPT DIAGRAM AND DECIDED NOT TO REQUEST RWY 5R. THE CAPT LATER CONFIDED THAT HE THOUGHT WE WERE CLRED TO FOLLOW THE ACFT. THAT ACFT WAS CLRED BY TWR TO TAXI TO RWY 5R.

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.