Narrative:

I was instructed when I arrived at work that I would be providing training on LC1 (local control) once my trainee arrived. Since he had not; I was assigned to work LA1 (local assist) until that time. We were in a single runway north flow configuration due to poor braking action/snow removal on runway 35R. There were roughly four in the pattern with several more VFR inbounds and numerous departures. I witnessed LC1 instruct aircraft X to line up and wait runway 35L while aircraft Y was on landing roll out. LC1 instructed aircraft Y to exit at A4 and contact ground. The pilot read back A3 (LC1; controller in charge; and myself missed the incorrect read-back). Before aircraft Y had exited the runway; LC1 cleared aircraft X for takeoff. I immediately pointed out that aircraft Y was still on the runway. A few other transmissions occurred before LC1 cancelled aircraft X's takeoff clearance. There was quite a bit going on at the time. The pilot appeared to be either still in takeoff roll or possibly already airborne at a very low altitude above the runway; and questioned LC1 if the cancellation of clearance was for them. At the time aircraft X was cleared for takeoff; aircraft Y was approximately 2000 feet down the runway. After clearly seeing that aircraft X had become airborne LC1 instructed the pilot to turn left to avoid any flyover. From my vantage point; it appeared that aircraft Y's position on the runway was possibly blocked by a window frame in the tower.a better scan of the entire runway surface could have prevented this from happening. Additionally; the local control was a more senior controller and I didn't want to appear too pushy as a la; however I probably should have spoken up a little louder; because I'm not quite sure that I was initially heard when I pointed out the conflict on the runway.

Related reports:

Google
 

Original NASA ASRS Text

Title: GFK Tower Controllers reported an aircraft was cleared for takeoff while the preceding arrival was still on the runway.

Narrative: I was instructed when I arrived at work that I would be providing training on LC1 (Local Control) once my trainee arrived. Since he had not; I was assigned to work LA1 (Local Assist) until that time. We were in a single runway north flow configuration due to poor braking action/snow removal on Runway 35R. There were roughly four in the pattern with several more VFR inbounds and numerous departures. I witnessed LC1 instruct Aircraft X to line up and wait Runway 35L while Aircraft Y was on landing roll out. LC1 instructed Aircraft Y to exit at A4 and contact ground. The pilot read back A3 (LC1; CIC; and myself missed the incorrect read-back). Before Aircraft Y had exited the runway; LC1 cleared Aircraft X for takeoff. I immediately pointed out that Aircraft Y was still on the runway. A few other transmissions occurred before LC1 cancelled Aircraft X's takeoff clearance. There was quite a bit going on at the time. The pilot appeared to be either still in takeoff roll or possibly already airborne at a very low altitude above the runway; and questioned LC1 if the cancellation of clearance was for them. At the time Aircraft X was cleared for takeoff; Aircraft Y was approximately 2000 feet down the runway. After clearly seeing that Aircraft X had become airborne LC1 instructed the pilot to turn left to avoid any flyover. From my vantage point; it appeared that Aircraft Y's position on the runway was possibly blocked by a window frame in the tower.A better scan of the entire runway surface could have prevented this from happening. Additionally; the LC was a more senior controller and I didn't want to appear too pushy as a LA; however I probably should have spoken up a little louder; because I'm not quite sure that I was initially heard when I pointed out the conflict on the runway.

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.