I have 0 experience since I am still in Flight School. But a friend of mine used to fly for Hageland Aviation Services which is apart of the Ravn Alaska brand. From what I understand, Ravn Alaska itself is Part 121, whereas Hageland and Frontier Flying are Part 135. I just talked to him about this yesterday, and he told me there is a current investigation on Hageland and Frontier due to recent crashes. He said their insurance company is probably going to pull their certifications. That's really all I know, but I figured I'd share.