Narrative:

I was the instructor on local control. My trainee was new. Toward the end of our session; the opportunity came to use luaw (line up and wait). After aircraft Y landed; my trainee instructed aircraft X to luaw. There was also an aircraft in left closed traffic. I told my trainee that he had to issue traffic; and could have combined instructions with traffic. My trainee then told aircraft Y to exit at taxiway charlie. I started to tell my trainee that he could have just waited and cleared aircraft X with anticipated separation instead of using luaw and that it would have actually been faster and use less transmissions. I didn't get the chance to say all of that until later. As soon as I said 'you could have cleared aircraft X' (literally four seconds after he issued exit instructions to aircraft Y); my trainee cleared aircraft X for takeoff with aircraft Y still on the runway. I immediately said no and told him to cancel the takeoff clearance. It was exactly two seconds from when my trainee cleared aircraft X; to when he canceled the clearance. Aircraft X might have had radio problems; he did on ground control a few minutes earlier; it's a loud airplane; and my trainee spoke really fast when canceling. Aircraft X did not hear the cancelation. My trainee tried again; and I stepped in to try a few times; aircraft X did not respond; until he was already airborne around the intersection of the runways. Just as aircraft Y was exiting the runway at a taxiway. There was about 2000 ft between them when aircraft Y exited the runway. I gave the brasher warning to the pilot and told the supervisor and controller in charge (controller in charge). We got relieved; and went to debrief all of the rules of luaw immediately.

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Original NASA ASRS Text

Title: ARR Tower Controller conducting on the job training reported observing a trainee clear an aircraft for takeoff while a landing aircraft was still on the runway.

Narrative: I was the Instructor on Local Control. My trainee was new. Toward the end of our session; the opportunity came to use LUAW (Line Up and Wait). After Aircraft Y landed; my trainee instructed Aircraft X to LUAW. There was also an aircraft in left closed traffic. I told my trainee that he had to issue traffic; and could have combined instructions with traffic. My trainee then told Aircraft Y to exit at Taxiway Charlie. I started to tell my trainee that he could have just waited and cleared Aircraft X with anticipated separation instead of using LUAW and that it would have actually been faster and use less transmissions. I didn't get the chance to say all of that until later. As soon as I said 'you could have cleared Aircraft X' (literally four seconds after he issued exit instructions to Aircraft Y); my trainee cleared Aircraft X for takeoff with Aircraft Y still on the runway. I immediately said no and told him to cancel the takeoff clearance. It was exactly two seconds from when my trainee cleared Aircraft X; to when he canceled the clearance. Aircraft X might have had radio problems; he did on ground control a few minutes earlier; it's a loud airplane; and my trainee spoke really fast when canceling. Aircraft X did not hear the cancelation. My trainee tried again; and I stepped in to try a few times; Aircraft X did not respond; until he was already airborne around the intersection of the runways. Just as Aircraft Y was exiting the runway at a taxiway. There was about 2000 ft between them when Aircraft Y exited the runway. I gave the brasher warning to the pilot and told the supervisor and CIC (Controller in Charge). We got relieved; and went to debrief all of the rules of LUAW immediately.

Data retrieved from NASA's ASRS site 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.