Casadastraphobia 

A fear of falling toward the sky. Its root may be a fear of isolation, or isolophobia. This phobia may extend to a fear of air travel, a fear of looking toward the sky, or a fear of being surrounded by the sky's reflection. In worse cases it may extend to a fear of going outside.

Evrae looks toward the sky. "Oof" he announces as if losing his breath, while quickly looking down. "What's wrong?" his friend Gemini asks. "I have Casadastraphobia." he responds. Gemini eyes him curiously "What was that?." He looks up at her "Oh, it's a fear of falling toward the sky. Sorry, I just get a little bugged out when I look up every now, and then."

Casadastraphobia by Srž Tanjur December 10, 2008

Casadastraphobia 

Fear of falling into the sky, originally coined on Urban Dictionary by user Srz Tanjur. Symptoms may include fear of being surrounded by tall buildings, fear of walking on floors that reflect the ceiling, fear of looking up, fear of being surrounded by the sky, fear of aircraft, and in sever cases fear of leaving the house and being outside.

"Why won't you stop clinging to the floor? You look ridiculous."
"I have Casadastraphobia- I can't help it."

Casadastraphobia by sovereignUniverse September 22, 2018