How often FAA require airlines to check metal fatigue?

It depends on the airplanes. All airplanes have a rigorous maintenance schedule that is more than enough to make sure you are safe. Aircraft operated for hire in the US have 100-hour inspections, annual inspections, special inspections required by that aircraft, special inspections of any part that has wear and tear, and major overhauls that are conducted after a certain amount of landings or hours (A/B/C/D, etc) checks... these are EXTENSIVE. Most of these test for fatigue of critical parts. Also, rest ured that modern aircraft are tested (the wing spars) to at least 150% of any stress they are certificated to sustain. Here's a video of this test on the 777 a href="http://www.youtube.com/watch?v=6Uo0C01Fwb8" rel="nofollow"http://www.youtube.com/watch?v=6Uo0C01Fw…/a Furthermore, before every flight and after every flight, pilots give a thorough preflight of the aircraft.