Way back, I believe the first jet passenger jet was the Lockheed
Electra. The plane mysteriously fell out of the air and very thorough
search for a cause was instituted. In the end, again if I remember
correctly, the conclusion was that the wing spar failed from fatigue
because the wing was nutating, a slight circular motion due to
gyroscopic effects.

Maybe that's the same thing caused the FL seaplane crash.