Thanks for all the replys! It's not that I am planning to do so but just find it unbelievable that the airliners e.g. out of LAX to the north or east fly absolutely unprotected from 10000ft to FL180. A wonder that nothing ever happened... Don't want to think what happens when a 757 hits a C172 mid air.
But seems to be no problem, otherwise there would be at least a Charly corridor for the big ones to climb/decent.