Narrative:

I was on duty working local control during a relatively slow time. I cleared a B737 to land runway 26R. A while later, I cleared a B737 for takeoff on runway 26R. The arrival then advised me that he was short final. (I had allowed myself to become distraction.) I immediately canceled takeoff clearance to B737 who then advised he was, or may have been, past hold bar. I immediately sent arrival B737 around to ensure separation. It was fortunate that the arrival B737 was alert and paying attention. Something I should have been doing. Major lesson learned! Corrective actions: cannot allow myself to get distraction when traffic is slow. Slow periods can be as bad as busy traffic periods if you don't pay attention.

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Original NASA ASRS Text

Title: AFTER CLRING A B737 TO LAND ON RWY 26R AT ONT AND A SHORT TIME LATER CLRS A B737 FOR TKOF ON THE SAME RWY.

Narrative: I WAS ON DUTY WORKING LCL CTL DURING A RELATIVELY SLOW TIME. I CLRED A B737 TO LAND RWY 26R. A WHILE LATER, I CLRED A B737 FOR TKOF ON RWY 26R. THE ARR THEN ADVISED ME THAT HE WAS SHORT FINAL. (I HAD ALLOWED MYSELF TO BECOME DISTR.) I IMMEDIATELY CANCELED TKOF CLRNC TO B737 WHO THEN ADVISED HE WAS, OR MAY HAVE BEEN, PAST HOLD BAR. I IMMEDIATELY SENT ARR B737 AROUND TO ENSURE SEPARATION. IT WAS FORTUNATE THAT THE ARR B737 WAS ALERT AND PAYING ATTN. SOMETHING I SHOULD HAVE BEEN DOING. MAJOR LESSON LEARNED! CORRECTIVE ACTIONS: CANNOT ALLOW MYSELF TO GET DISTR WHEN TFC IS SLOW. SLOW PERIODS CAN BE AS BAD AS BUSY TFC PERIODS IF YOU DON'T PAY ATTN.

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.