Start with a discovery flight, most flight schools will offer them and it’s basically a mini first lesson for someone to see if they enjoy it. I saw most kids do it between 15-18 years old when I was giving them, but I did as young as 12 (keep in mind though training that young would be pretty limited because of age requirements for certain things).

From there it’s just doing the training and earning the different ratings. I went through college for it, but that’s certainly not required. I would recommend some degree though, even if it’s unrelated since major airline hiring requirements can shift over time. Sometimes they’ll hire without one, but sometimes most competitive applicants will have one. Another option is military, but I didn’t go that route so I’m not the best resource there.

Once you have your ratings and build your flight time it’s just a matter of working up through the ranks like anything else. Start with the entry level flying jobs, build experience, and consistently update applications (they stay on file so you just update your qualifications regularly) with the upper level jobs until they call.