Like he’s obligated to cooperate with the investigation but he’s within his rights to just say “hey this feels like a witch hunt I am not participating or giving statements at all” and it’s not clear how much they really would have done.
Absolute certainty he’d lose his license maybe there’s penalties or fines for stonewalling the investigation, but like it would probably blow over as long as they made sure he never got near the controls of an airplane again.
But then he decided to obstruct a federal investigation. Like that’s the one thing you really can’t do ask Martha Stewart.