You may be reluctant to drink a lot of water before a flight because of the lack of in-flight facilities. Instead, you may drink a big cup of coffee right before you take off to help you stay alert. But caffeine is a diuretic, so not only does it make you want to go to the bathroom more, it also makes you more dehydrated. With no air conditioning in the airplane, the cockpit gets hot and you climb up to altitude, exacerbating the problem.
The first symptom of dehydration is thirstiness, but you can’t rely on your body’s ability to tell you to drink. Unfortunately your body doesn’t tell you to replenish your fluids until it is already too late. Just a small amount of liquid will eliminate your desire to drink. But it won’t hydrate you enough. It will simply shut off the thirst reflex.
