I used to work in aerospace. Airliners made from aluminum alloys have a definite fatigue life. Past a certain number of cycles, they’re no longer trustworthy without extensive inspections and/or overhaul (to include re-skinning or replacement of structural members). I’m not that familiar with carbon fiber composites, but I’ve heard that properly designed and fabricated composites are stronger by weight than steel, and have have better fatigue life than aluminum alloys. I’m sure the 787 structures have been extensively tested at the coupon, and airframe level to validate predicted life; that’s how we did it in the rocket engine business. I would be more than willing to fly on a 787 versus an old plane. Remember the Aloha Airline 737 that turned into an open top airplane? That’s metal fatigue in action.
My passion is old airplanes(metal)restorations namely B-17s.The plane we are working on now just turned 70 years old and is still going strong.70 years.You wont see that with the plastic birds.I’ll dance with the one that brung me.:)