2 Years ago, after an WU I noticed, that if I wanted to start a flight and clicked on the “Fly” button, the game went CTD. In the end, the cause was an bugged freeware livery. I removed that and no more issues.
I also found an thread on this forum about imediate CTD when Clicking the “Ready to Fly” Button with No Error where faulty keybindings were the cause.