advantages and disadvantages using air substrate

Dear all
My name Evyta, and I'm Beginner making antenna
I try to make antenna for my assignment in college, and there's something confusing me, and i want to ask it to all of you.
I hope you wanna spend your time answering my Question.

What is the advantages and disadvantages using Air as Substrate in Microstrip antenna.

Thank you, and I'll be waiting for your reply.

Best Regards

Evyta

is there anyone outside want to explain about advantages and disadvantages using Air as Substrate in Microstrip Antenna?

Help me please :(

If I remember right, Normally air substrate should have low insertion loss.