I have New daily persisitent headaches, chronic daily headaches, migraines,cervicogenic headaches, and myofascial pain syndrome. I fly every couple of months in a small prop airplane that isn't pressurized. I have noticed that when I have a flareup, it improves within a half an hour or so of being in the air. It isn't instant relief but a gradual lessening of pain. The relief will last anywhere from a couple of hours up to 24 hours or so. Does anyone know why?