air marshal vs sky marshal

air marshal and sky marshal both are nouns.

Word	Noun	Adjective	Verb	Adverb
air marshal	Yes	No	No	No
sky marshal	Yes	No	No	No

As nouns, air marshal and sky marshal are synonyms defined as:

air marshal and sky marshal: a person trained by the government in hijacking and terrorist tactics who (for security reasons) is a passenger aboard an airline flight

air marshal (noun)	sky marshal (noun)
a person trained by the government in hijacking and terrorist tactics who (for security reasons) is a passenger aboard an airline flight	a person trained by the government in hijacking and terrorist tactics who (for security reasons) is a passenger aboard an airline flight