I think that some is and some isn't. I used Rustoleum clear on a plane. What a beautiful finish it gave. The beauty wore off after the first flight. Now after I bring it home after a day at the field I clean it with mineral spirits to get the gum off.

But, I tested and finished a cowl with Rustoleum black and it has held up great. So buyer beware! Test your color carefully before applying to a plane!