The Air Force now has a two year program but unless you are already a sophomore, you are much better off doing all four years. As a non scholarship cadet, you can leave AF Rotc without consequences after you finished your second year. In the summer between Sophomore and Junior year, assuming you are selected, you attend AF Field Training or Lead as it now called. Assuming you pass (almost everyone does), when you go back to school for Junior year, you will contract with the Air Force and you will commission when you graduate. For the basic job, you will serve for 4 years. If you become a pilot, you will serve for minimum of 11 years ( 1 year of flight school and 10 years of Active duty) Depending on the job, it can be anywhere from 4 -10 years. As for grades, as long as you are a 3.0 you will be fine. Of course the more popular the position (pilot) the better the GPA should be. My son however, got a pilot spot but had a 3.0 GPA. He did very well on the other things they look at. They look at your GPA, they look at your AFOQT (sort of SAT but includes pilot and navigation skills), how well you score on your Physical fitness test, your rating from your commander and how well you did at Field Training (Leads) Some of the positions are Rated, which include Pilot, RPA (dones) Combat Systems officer (navigator) and Air Battle Manager. You go up before a board where they review your qualifications and choose you for those positions. All of the other positions are non-rated and to be honest no sure how those works, but you select what positions you want and I would imagine based on your major and other qualifications they assign them