What to do after finishing high school to work as an airline pilot?

Go to college and get a degree. At the same time, slowly work towards getting your private pilot's license, followed by an instrument rating, then your commercial license, then your instructor's rating. When you graduate from college, you get a job as a pilot instructor. Once you have worked as an instructor for about 2-3 years and have built up at least 1500 hours, you can start applying at regional airlines. after making many professional connections and building several years of experience, you can start applying at the major airlines. Most airlines want you to have at least a bachelor's degree, but it can be in any subject, but it is important to get a degree.