Personally, I doubt I could have made it through airline selection aged 18 or 19. I simply didn't have the maturity or life-experience. Being 30-something gives you a lot more to talk about at an interview.
That said, there are plenty of youngsters out there who are perfectly capable of landing an airline job. I've trained with some of them, and their flying skills and maturity are very, very impressive. As regards life-experience, I do know one 20 year old airline pilot who thinks that buffalos have wings, and he still managed to get the job . . .
