An "airhead" is...

According to the American Heritage Dictionary, the term "airhead" has two definitions:

air-head1 (ar'hed) n. A silly, stupid person.
air-head2 (ar'hed) n. An area of hostile territory secured by paratroopers.

But, I think that we should add a third definition for the word, "air-head," as it is used on this Web site:

air-head3 (ar'hed) n. A person who is an aviation or airshow enthusiast.