Some believe that a fear of flying is a distinct phobia unrelated to anything else. Others believe that this phobia is actually a combination of other phobia such as a fear of heights, known as acrophobia, or a fear of enclosed spaces, known as claustrophobia. Some have suggested that a fear of flying is linked to agoraphobia in which one is afraid of open spaces, such as can be found in the bright, blue skies. Fear of flying is a symptom of a problem, rather than a problem itself. There are many different causes for a fear of flying also.