Narrative:

Air carrier X was taxiing for takeoff runway 6R. He was 3000-4000 ft from the approach end of the runway (on the parallel taxiway) when I cleared him for takeoff runway 6R. Small transport Y called ready for takeoff on runway 24L. At the time he was crossing runway 24R at golf taxiway for an intersection departure. I called south radar to get a release for small transport Y, and cleared small transport Y for takeoff runway 24L. At that time I scanned runway 24L and observed air carrier X past the hold lines on subject's taxiway starting to enter runway 6R. I cancelled air carrier X's clearance for takeoff. I observed small transport Y past the hold lines on golf taxiway starting to enter 24L. I cancelled small transport Y's clearance for takeoff and instructed him to make a 180 degree turn and exit runway 24L. When small transport Y was off the runway I cleared air carrier X for takeoff runway 6R. My shift started at 0700 local and I was signed on position at 0700 local. The incident occurred at 0716 local. When small transport Y called ready I scanned my strip board and mistook air carrier X strip for an arrival that had just exited runway 6R. I did not realize my mistake until I scanned the runway and cleared small transport Y for takeoff. The situation was resolved before either aircraft had started takeoff roll, but both had started to enter the runway.

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Original NASA ASRS Text

Title: OPPOSITE DIRECTION TFC, CTLR CLRED ACR X AND SMT Y FOR TKOF ON SAME RWY. POTENTIAL LTSS.

Narrative: ACR X WAS TAXIING FOR TKOF RWY 6R. HE WAS 3000-4000 FT FROM THE APCH END OF THE RWY (ON THE PARALLEL TAXIWAY) WHEN I CLRED HIM FOR TKOF RWY 6R. SMT Y CALLED READY FOR TKOF ON RWY 24L. AT THE TIME HE WAS XING RWY 24R AT GOLF TAXIWAY FOR AN INTERSECTION DEP. I CALLED S RADAR TO GET A RELEASE FOR SMT Y, AND CLRED SMT Y FOR TKOF RWY 24L. AT THAT TIME I SCANNED RWY 24L AND OBSERVED ACR X PAST THE HOLD LINES ON SUBJECT'S TAXIWAY STARTING TO ENTER RWY 6R. I CANCELLED ACR X'S CLRNC FOR TKOF. I OBSERVED SMT Y PAST THE HOLD LINES ON GOLF TAXIWAY STARTING TO ENTER 24L. I CANCELLED SMT Y'S CLRNC FOR TKOF AND INSTRUCTED HIM TO MAKE A 180 DEG TURN AND EXIT RWY 24L. WHEN SMT Y WAS OFF THE RWY I CLRED ACR X FOR TKOF RWY 6R. MY SHIFT STARTED AT 0700 LCL AND I WAS SIGNED ON POS AT 0700 LCL. THE INCIDENT OCCURRED AT 0716 LCL. WHEN SMT Y CALLED READY I SCANNED MY STRIP BOARD AND MISTOOK ACR X STRIP FOR AN ARR THAT HAD JUST EXITED RWY 6R. I DID NOT REALIZE MY MISTAKE UNTIL I SCANNED THE RWY AND CLRED SMT Y FOR TKOF. THE SITUATION WAS RESOLVED BEFORE EITHER ACFT HAD STARTED TKOF ROLL, BUT BOTH HAD STARTED TO ENTER THE RWY.

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.