I am not an expert on the military side of things but I did have a friend who went through it several years ago. For the Air Force, I believe he signed a minimum 10 year commitment. He had to have a 4 year college degree and go through testing with the Air Force. He scored well enough to be offered a fighter pilot position and flew F-15s for about 11-12 years.

The majority of pilots getting hired at the majors are in their 30s. By the time you finish your degree, and serve your time in the military, you would be ripe pickings for the majors.