From Longman Dictionary of Contemporary Englishairheadair‧head /ˈeəhed $ ˈer-/ noun [countable] informal someone who behaves in a stupid way
Examples from the Corpus
airhead• He treats his women staff as if they're all airheads.• Is she a grasping airhead or a complete naif?• Then some overpaid TV airhead starts telling us how wonderful her producer is. 