Marine Aviation selectees are chosen by a board, just like Navy guys, and find out during service selection night in February of Firstie year. To be competitive, you have to have attended Leatherneck, which is 4 weeks of Marine ground type stuff in Quantico during the summer and gotten good apptitude grades while there. PT scores factor into it, as well as Grades, Military Performance, Conduct, ECA's etc. There are 41 slots this year, and about 110 people signed up for it.