I don't advocate using anything for air lines. Air was meant to be free...not contained. Just like chickens!

But, other than that, I know a guy that wanted to do some "MythBusters" type stuff on PEX when he first heard about it being talked about for airline. So-this guy took a 4' length of PEX & put fittings on it. Plugged off one end...rigged other end w/air chuck fitting. Then, pressurized it to 150# & used a valve to contain air in PEX. Then this guy took this pressurized piece of PEX & beat hell out of it w/a hammer on an anvil. He put it in a vise & tried to make it burst by crimping. Then he laid it on anvil & beat on it w/8# sledge. He bent it in 1/2 & beat on it some more. He put it in freezer & froze it. It crimped...it creased...but it never burst. He said that was good enough for him. He couldn't imagine abusing airline more.

I think this guy is using PEX for airline now. I don't recommend it however.