Aircraft X executed a good aircraft report when aircraft Y non-adherence to ATC clearance resulted in it taxiing into position on an active runway without clearance.

Narrative

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

I was making a visual approach and tower cleared us to land. Our altitude was approximately 400 feet when an aircraft Y that had been holding short of the runway on which we were cleared to land, taxied onto the approach end of the runway.

I confirmed the situation with the captain and we both agreed on a good aircraft report. During the good aircraft report, we informed tower what we were doing. Tower then cleared us to make left traffic. We completed the good aircraft report procedure. We were again given landing clearance and the flight concluded normally.

Callback conversation with reporter revealed the following info: The reporter stated the aircraft that taxied onto the runway was an aircraft light and the aircraft had not been instructed to taxi onto the runway. Reporter's aircraft was landing on the left runway.