If you want to get your ATP certificate you're going to need A LOT more training than a Private Pilot license. I'll be taking my PPL check ride next week just under 45 hours. If you want to make it to the big leagues and fly airliners you should do a lot more research. After your Private you'll need an instrument rating, commercial rating, and multi-engine rating. To get all those can take minimum about a year if you GM Tech 2 fly full time. After that you'll need to get an instructors rating, airliners prefer getting instrument private and commercial, and then you'll have to instruct for at least a year to build up hours. You'll need 1500 hours total logged and then 500 hours cross country to get an ATP certificate.

To apply for a regional airline you're going to need a minimum of 700 hours, but with a new law taking affect next year in August you'll need a minimum of 1500 hours to apply for a regional airline and that's just to fly right seat (first officer). Also you might want to look at getting a college degree because it will be hard to get hired by the big guys later on in life if you don't have a degree. You can go to an FAA approved University and get a degree in aviation and that will give you all the ratings you need then you'll have to spend at least a year instructing to get the hours, which is what I'm doing.

To apply for the big guns like United, Delta etc. you're going to Tech 2 Scanner need about triple the amount of hours you need for a regional airline and TONS of jet experience. Take into account also average salary for a regional airline is just under 30k a year, so don't be expecting the big bucks for a while!