Air - As the main structural element

Fanciful was the word I used to describe this notion…

Can you provide an example of how this works? A reference, a diagram, a calculation?
Is it about air as a structural element?

Is a ram air kite heavier when filled with high pressure air at high speed … Or when hung limply from a string in the air?

If you take fire safety seriously then chemical reactions with air are not fanciful.