air
noun [ U ]
uk/eər/ usby air
TRANSPORT
travelling by or using planes:
arrive/travel by air 25% of the state's economy is fueled by tourists who travel by air.
deliver/send/ship sth by air The company adds a surcharge for express packages delivered by air.
up in the air
if a matter is up in the air, it is uncertain and no final decision has been made about it:
The future of the company has been up in the air since one of its key shareholders was compelled to sell its stake.