question for a book I'm writing: how easy would planes be to mess up in such a way no issues appear until plane takes off?
https://en.wikipedia.org/wiki/National_Airlines_Flight_102
https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261
https://en.wikipedia.org/wiki/Japan_Air_Lines_Flight_123
The last one was caused by a bad repair from a tail strike seven years earlier.
Read some NTSB documents about crashes especially ones where “maintenance” appears.