It's not easy. There are two ways to become a 67J, the MOS of an aeromedical evacuation officer. The first is that you have go to a commissioning source and be an officer in the US army through west point, ROTC, or OCS. Once you have branched medical service corp, you can then apply to be a medevac pilot. The application is due usually around 01MAR. The second way is to become a warrant officer and your airframe must be blackhawk. Toward the end of flight school, you can request/apply to become a commissioned officer, 2LT, and go from a WO to an 2LT as a 67J. For the past few years, they pick about 25-30 every fiscal year.
