Up in the air means still undecided, with nothing settled yet. Everything is up in the air, plans are up in the air, leave it up in the air.
It describes the state of a plan rather than anybody's feelings about it. The picture is of something thrown and not yet landed.
1phraseup in the airStill undecided; nothing is settled yet.
“The date is still up in the air until the hall confirms.”
up in the air is a phrase.
Practised in Idioms