airhead vs bridgehead

airhead and bridgehead both are nouns.

Word	Noun	Adjective	Verb	Adverb
airhead	Yes	No	No	No
bridgehead	Yes	No	No	No

As nouns, bridgehead is a hypernym of airhead; that is, bridgehead is a word with a broader meaning than airhead:

airhead: a bridgehead seized by airborne troops
bridgehead: an area in hostile territory that has been captured and is held awaiting further troops and supplies

Other hypernyms of airhead include foothold.

airhead (noun)	bridgehead (noun)
a bridgehead seized by airborne troops	an area in hostile territory that has been captured and is held awaiting further troops and supplies
a flighty scatterbrained simpleton	a defensive post at the end of a bridge nearest to the enemy