The odds of you getting “there in five years” for a regional job is fully achievable. But not for a major airline job. You could actully make it to a regional by 19. It just takes a lot of effort and focus.

As others have cautioned there’s no guarantee, especially as a 16 yr old, that the job is really what you’ll be satisfied with. If you enjoy it by all means chase it. If you realize it’s not for you change course. There is no point in being miserable, of second guessing yourself, for your entire adult life.