For many people, fear of flying has nothing to do with worrying about the airplane crashing. Rather, flying triggers claustrophobia, which is a fear of being trapped in small, enclosed places such as an airplane cabin.

Claustrophobia is an anxiety disorder characterized by an irrational fear of enclosed or small spaces, says the Diagnostic and Statistic Manual of Mental Disorders. A claustrophobic patient does not fear being in closed spaces, but the negative consequences of being in that place.