tailwind vs air current

tailwind and air current both are nouns.

Word	Noun	Adjective	Verb	Adverb
tailwind	Yes	No	No	No
air current	Yes	No	No	No

As nouns, air current is a hypernym of tailwind; that is, air current is a word with a broader meaning than tailwind:

tailwind: wind blowing in the same direction as the path of a ship or aircraft
air current: air moving (sometimes with considerable force) from an area of high pressure to an area of low pressure

Other hypernyms of tailwind include current of air, wind.

tailwind (noun)	air current (noun)
wind blowing in the same direction as the path of a ship or aircraft	air moving (sometimes with considerable force) from an area of high pressure to an area of low pressure