Tower ground controller intervenes when local controller trainee clears a PA31, midfield, for takeoff prior to a previously cleared for takeoff DH8 has passed the PA31's position.

Narrative

Rewritten in plain English from NASA’s original all-caps telegraphic report — facts, figures, and terminology preserved.

Aircraft X (a Dash 8) was cleared for takeoff on runway 16L. Aircraft Y (a PA31) was told to taxi into position and did so at Intersection N. The ground controller noticed two aircraft on the departure runway and advised the local controller. The local controller trainee then aborted the takeoff roll of Aircraft Y. The aircraft were separated by approximately 1/2 mile on the runway.

Supplemental info from ACN 425033: On January XA, 1999, I was on a flight from SEA to CLM. I was holding short at runway 16L, Intersection N, when, to the best of my knowledge, I was cleared for takeoff. I read back the clearance to the tower, and as I crossed the holding short line, the tower made a call for the aircraft at Intersection N to clear the runway and go back on the taxiway. So I complied and did as instructed. Later, the tower advised me that the clearance was for another flight at the end of runway 16L. After that, the tower cleared me for takeoff and notified me to call the SEA tower supervisor.