Stress
You're constantly flying thousands of feet above the ground—as safe as air travel is, yeah, it can tend to be stressful. Of course, the longer you're on the job, the more your theoretically precarious scenario will become an afterthought.
But you'll also have the stress of money troubles, homesickness, and picky and irritating passengers. Too bad you won't be able to afford all those psychiatry bills that keep piling up on your kitchen table....