I know guys who left North West for TWA and Pan Am in the early 1980's. This industry is too unstable to try to guess which carrier is going to be around in 10-20 years.
What looks like a sure thing today could be seen as a huge blunder in 5 years, given a new CEO, a Merger, a Bankruptcy, etc. Nobody has a crystal ball that works 100% of the time.
It's a crap shoot.
Roll the dice and hope for the best and then don't drive yourself crazy thinking "I could'a, should'a, would'a."