If someone non-current/recent goes to a regional, 6 months to sitting in indoc as a newhire at a major would be a very optimistic timeline.

With a 2-3 month training timeline, that only leaves 3+ months to get your 100 or 200 hour lookback, get an interview call, ace the interview, and then class up at a major.

It would be realistic to be getting the major interview calls by the 6 month mark, but then however long the interview/background check/class assignment timeline takes after that.