This study examined pilots' vigilance during an extended general aviation flight as measured by their capacity to exercise control over the aircraft during a planned flight. Thirty-one qualified pilots flew a flight simulator from Wagga Wagga to Bankstown, Sydney, a distance of 207 nautical miles. The flight comprised five separate legs, although three legs were subjected to analysis. On the basis of attentional resource theory, it was hypothesised that task performance would differ based on the requirement for memory retrieval. Consistent with the hypothesis, the results revealed a deterioration in those tasks for which there was a substantial requirement for memory retrieval. Further analysis revealed that the deterioration in performance was best predicted by pilots' perception of the workload associated with the flight and their perception of their ability to exercise control over aircraft during normal conditions. The implications are discussed in terms of system design and training.