Narrative:

I was working local control and the airspace was moderately busy. I had been on position about 20 minutes already; so not too long. I first talked to an aircraft that was on the GPS-a approach into mri. I directed him to circle south direct west high and then enter left downwind for 25. I cleared an aircraft for a touch and go clearance on runway 25. Traffic continues and in my scan I notice he is about a mile south of west high in lake hood's airspace so I call lake hood and point him out. In the GPS-a aircraft correction; he is due straight north towards ship creek. I correct him to make left traffic and so he makes a circle 360 and enter left downwind. I get a call that aircraft Y is ready to cross runway 25 at taxiway delta. I tell aircraft Y to hold short of runway 25 for traffic on short final (aircraft on touch/go clearance). He reads back correctly. Aircraft X calls ready to depart 25. I tell him to hold short of runway 25 traffic is on short final. He reads back 'hold short 25 at kilo; aircraft X'. After the touch and go passes the threshold for runway 25; I clear aircraft X to 'runway 2-5 line up and wait' and he reads back 'line up and wait 25; aircraft X.' I transmit to aircraft X; 'and aircraft X; traffic will be crossing downfield'. After the touch and go aircraft is done and airborne again; I clear them to make right traffic (to remain clear of the 'lost' GPS-a aircraft in the left pattern). My next transmission to aircraft Y; 'aircraft Y; cross runway 25 at delta; traffic holding in position full length.' aircraft Y reads back 'crossing 25 at delta; aircraft Y; expediting.' I was scanning between and watching the aircraft cross the runway when I hear my controller in charge 'he's rolling; he's rolling!' at this point; I observed aircraft X in departure roll nearing taxiway hotel without a takeoff clearance and I transmitted 'aircraft X; hold position.' he reads back; 'hold position; aircraft X.' we estimate he was as little as 1850 feet from the taxiway aircraft Y was crossing at. I advised aircraft X to 'turn left at hotel and contact ground unless you can take departure from current position.' he opted to depart from where he was at on the runway; which was between taxiway juliet and taxiway hotel; definitely closer to hotel though because that's the intersection I departed him from. I told him 'aircraft X; from current position runway 25 at hotel cleared for takeoff; unable altitude deviation' and then he departed. I cleared the GPS-a aircraft to land; and worked a couple other aircraft before giving aircraft X a brasher warning. The brasher warning was given before switching him to departure.there was never any imminent danger of the two aircraft involved hitting or any damage caused. It was just a mere fact that there was two aircraft on runway 25 at the same time and one wasn't doing what he was cleared to do. I think the pilot of aircraft X had an expectation bias because often they are just cleared for takeoff and don't have to wait to depart. He read back the lineup and wait clearance like he should have and I think he just had a brain [lapse]. I would just recommend that he be prudent when listening for clearances. On my part; I was scanning; but not in the right place at the right time. I was watching aircraft Y as he crossed to the other side of the runway; verifying he was clear of the runway; so I then I could clear aircraft X for takeoff. I would also recommend a controller in charge (and other tower team members) be as attentive as possible; because if mine hadn't been at the time; it would have been a few seconds later and the departing aircraft could have been airborne. I would have noticed a few seconds later after observing aircraft Y clear of runway 25 upon my takeoff clearance to aircraft X. This is a good example of 'see something; say something' coming into play to. Because of this mentality; I knew as soon as I could that aircraft X was rolling.

Related reports:

Google
 

Original NASA ASRS Text

Title: MRI Tower Controllers reported an aircraft attempted to depart when it had been instructed to line up and wait. Traffic was crossing the runway downfield.

Narrative: I was working local control and the airspace was moderately busy. I had been on position about 20 minutes already; so not too long. I first talked to an aircraft that was on the GPS-A Approach into MRI. I directed him to circle south direct West High and then enter left downwind for 25. I cleared an aircraft for a touch and go clearance on Runway 25. Traffic continues and in my scan I notice he is about a mile south of West High in Lake Hood's airspace so I call Lake Hood and point him out. In the GPS-A aircraft correction; he is due straight north towards Ship Creek. I correct him to make left traffic and so he makes a circle 360 and enter left downwind. I get a call that Aircraft Y is ready to cross runway 25 at taxiway Delta. I tell Aircraft Y to hold short of runway 25 for traffic on short final (Aircraft on touch/go clearance). He reads back correctly. Aircraft X calls ready to depart 25. I tell him to hold short of runway 25 traffic is on short final. He reads back 'Hold short 25 at Kilo; Aircraft X'. After the touch and go passes the threshold for runway 25; I clear Aircraft X to 'Runway 2-5 Line up and wait' and he reads back 'Line up and wait 25; Aircraft X.' I transmit to Aircraft X; 'And Aircraft X; traffic will be crossing downfield'. After the touch and go aircraft is done and airborne again; I clear them to make right traffic (to remain clear of the 'lost' GPS-A aircraft in the left pattern). My next transmission to Aircraft Y; 'Aircraft Y; Cross runway 25 at Delta; traffic holding in position full length.' Aircraft Y reads back 'Crossing 25 at Delta; Aircraft Y; expediting.' I was scanning between and watching the aircraft cross the runway when I hear my CIC 'He's rolling; he's rolling!' At this point; I observed Aircraft X in departure roll nearing taxiway hotel without a takeoff clearance and I transmitted 'Aircraft X; HOLD POSITION.' He reads back; 'Hold position; Aircraft X.' We estimate he was as little as 1850 feet from the taxiway Aircraft Y was crossing at. I advised Aircraft X to 'turn left at Hotel and contact ground unless you can take departure from current position.' He opted to depart from where he was at on the runway; which was between taxiway Juliet and taxiway Hotel; definitely closer to Hotel though because that's the intersection I departed him from. I told him 'Aircraft X; from current position Runway 25 at Hotel cleared for takeoff; unable altitude deviation' and then he departed. I cleared the GPS-A aircraft to land; and worked a couple other aircraft before giving Aircraft X a brasher warning. The brasher warning was given before switching him to departure.There was never any imminent danger of the two aircraft involved hitting or any damage caused. It was just a mere fact that there was two aircraft on runway 25 at the same time and one wasn't doing what he was cleared to do. I think the pilot of Aircraft X had an expectation bias because often they are just cleared for takeoff and don't have to wait to depart. He read back the lineup and wait clearance like he should have and I think he just had a brain [lapse]. I would just recommend that he be prudent when listening for clearances. On my part; I was scanning; but not in the right place at the right time. I was watching Aircraft Y as he crossed to the other side of the runway; verifying he was clear of the runway; so I then I could clear Aircraft X for takeoff. I would also recommend a CIC (and other tower team members) be as attentive as possible; because if mine hadn't been at the time; it would have been a few seconds later and the departing aircraft could have been airborne. I would have noticed a few seconds later after observing Aircraft Y clear of runway 25 upon my takeoff clearance to Aircraft X. This is a good example of 'see something; say something' coming into play to. Because of this mentality; I knew as soon as I could that Aircraft X was rolling.

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.