Dehydration is a concern when flying. Since there is a lower level of oxygen available, passengers tend to breathe faster and increase their water loss. It is best to try to drink 8 to 16 ounces of water before the flight departs and aim for at least 8 ounces for every hour on the flight. Consider limiting alcoholic or caffeinated beverages that may contribute to dehydration. Since people cannot take liquid beverages through security, hydrating is important before getting to the airport.