up in the air悬而未决；（计划、安排）不确定

I didn’t get into college, so my future is kind of up in the air.我没考上大学，所以我何去何从现在有点不确定。

Becky and I were supposed to go shopping this weekend, but things are up in the air now, because she’s not feeling well. Becky 和我本来这周末要去逛街的，但是现在不确定了，因为她现在身体不太舒服。