Flight operations can involve rapid multiple time changes and long, irregular work schedules. These factors can result in sleep loss, circadian disruption, and fatigue with subsequent effects on flightdeck performance. Countermeasures to reduce or mitigate the effects of these factors can be divided into two approaches: preventive strategies and operational countermeasures. Preventive strategies are used prior to a duty period to reduce or mitigate the fatigue created by flight and duty schedules. Operational countermeasures are used during flight operations to maintain performance and alertness. Naps can be used as both a preventive strategy and an operational countermeasure. Strategic napping in two different flight operation environments will be used to illustrate its application as a fatigue countermeasure. A recent NASA/FAA study examining the effectiveness of a preplanned cockpit nap to acutely improve alertness and performance on the flightdeck will be described.