When I fly, I don't drink a lot of water until I land, but if I'm flying for a few hours, that can lead to becoming dehydrated. I always tell passengers to drink a lot of water after they go flying. But I've discovered that if I drink only water, I still can end up with a dehydration headache. However, lately, I've been eating cashews while I'm hydrating and found that 100 percent of the time, I do not have dehydration headaches afterwards. I suppose the salt in the cashews help the body absorb water.