What does the idiom “up in the air” mean?

Correct answer: Uncertain. “Up in the air” means undecided or uncertain.

Background: The idiom describes plans that are not settled.

• Fly in the sky: It is not about flying in the sky.
• Sailing in air: It is not about sailing in the air.
• Climbing the mountain: It is not about climbing a mountain.

Did you know? Its opposite is “settled” or “set in stone”.

Memory trick: Up in the air = not decided.