You have a new top guy with deep skills and Industry connections, who is changing the way the company is doing things. It stands to reason that he's going to bring in his own folks on the executive level. That should be seen as a good thing.
As to the active operating posts, you're mixing apples and oranges by talking about the resignation of some people who worked under the old top guy. And you're seeing some people under the new guy, as he takes more control, finding other and better opportunities as Amerijet starts to be a credential that looks decent on a resume.
From a perspective way outside, this looks like a place that has lots of opportunity for people at all levels, but certainly isn't a stable predictable employer like a UPS. Some people thrive in one environment. Some people thrive in the other. Upheaval means opportunity. Complete stability means limitations on advancement. That's just the way it is. Most people like a combination of the two that yields their personally-desired combo of stability and opportunity, but those are kind of few and far between. It's a continuum, and Amerijet currently falls in one place on it. Hopefully, over the next few years, it'll move more to the other side of the spectrum as enthusiastic non-complainers jump into opportunity spots and try to make a difference, like your MEC, who fought hard for ALPA.