All humans go through their lives alternating between the states of sleep and wakefulness. The sleep state is further divided into non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS). The three states, NREMS, REMS, and wakefulness form a Troika of Consciousness Cycle (TCC). Mechanisms in the brain control sleep and alertness in a rhythmic manner, producing the same basic pattern every twenty-four hours, typically eight hours asleep and sixteen hours awake. This daily cycle, or circadian rhythm, is modified by external events: in particular by high-speed air travel traversing several time zones.
There is a need for better means of predicting the effects of air travel on the circadian rhythm so that travelers can better plan their activities to compensate for the changes which result from such travel.