uncertain vs up in the air

uncertain and up in the air both are adjectives.

Word	Noun	Adjective	Verb	Adverb
uncertain	No	Yes	No	No
up in the air	No	Yes	No	No

uncertain (adjective)	up in the air (adjective)
not established beyond doubt; still undecided or unknown	very uncertain
lacking or indicating lack of confidence or assurance	not yet determined
not certain to occur; not inevitable
not established or confirmed
ambiguous (especially in the negative)
not consistent or dependable
subject to change