Originally Posted by Nikolai

IIRC from my undergrad materials classes, aluminum is problematic in that it does not have a fatigue stress limit, whereas most other metals will plateau after a certain number of cycles. The obvious solution is over-engineering the frame, but at a weight penalty. Interesting case study the prof had told us about, a lot of early passenger jets were high-wing, but passengers would look out the windows and have a panic attack when the wing skin would be cracking under lift load...