The good part is failures before ATP seem a lot more forgivable. The bad part is 4 is already a lot and you really need to push for a clean record from here on out.

I know a couple pilots with several busted rides and other black marks that finally got the majors to interview them in the past few months (checkride busts + a 121 training failure or ac incident) . Both of them have CJOs at legacies and class dates canceled indefinitely because of covid. So it really remains to be seen if it will ever come to fruition for them. At some point it will get to the point again where Delta and United can't just skim the creme de la creme off the top of the app pool and they'll start looking at people aren't 'perfect' again. However, this covid recession probably set that back another 7-10 years. There's still a glut of highly qualified applicants, as people build more experience that number only gets bigger.

I also know a couple people that flowed up to AA that would have really struggled to get hired off the street.