Jet lag occurs when your body’s biological clock does not correspond with local time. This is common for international travelers and travelers who opt for red-eye flights across the U.S.
The condition of jet lag may last several days until one is fully adjusted to the new time zone, and a recovery rate of one day per time zone crossed is a suggested guideline. The issue of jet lag is especially pronounced for airline pilots, crew, and frequent travellers. Airlines have regulations aimed at combating pilot fatigue caused by jet lag.