Sorry about the highjack here ..... They require what's known as an "A & P" liscense. That is for "Airframe and Powerplant". I know about this as my father taught at East Coast Aero Tech in Bedford, MA (at Hanscom Field) for many years. They learn metal work and fabrication, jet and recip engines, electronics and electrical, hydraulics, pneumatics, woodworking and more and have to pass a rigorous test to get the FAA A&P liscense. I can't say who exactly needs this liscense, but I believe that any work done on a commercial airplane needs to be either performed, or signed off on, by someone with an A&P liscense. I'd guess that mtbikeinpa might know the exact details. Please fill in any omissions or correct any mistatement. Please keep in mind that I got most of this at the dinner table over many years. I will say that a lot of what I know about turning a wrench I got from my Dad.

A&P mechanics are not required to be liscensed pilots, but there are likely many who are. I can tell you that in the USAF aircraft are "tested" by the pilots. After every flight any discrepancies are noted in the debrief and a maintenance form filed. The "fixes" are checked in the next flight by the pilot and cleared if corrected. After certain periodic maintenance and major fixes FCFs (functional check flights)are performed and the aircraft is literally put through it's paces and checked to see if it is up to it's rated performance. I know about this as I worked in flight simulators and they were under the same regime of maintenance/inspections/checkouts as the actual aircraft. I would have to believe that civilian aircraft are maintained under a similar program, as, in the end, there is the question of what the Air Force calls "human reliability" - i.e. some person or persons lives are at stake if you don't do your job properly. In your case, Rev Chuck, one of the person's lives would be yours when those planes fly over your house ;-) So, hopefully, you will sleep a little better knowing that not just anybody is qualified to work on aircraft and deem them airworthy. Sorry for the tangents and verbosity, but that's just me.