if the military is footing the bill for his education, he owes time. the undergrad is usually 1:1, meaning one year of service for each year of education. he'll train in the summers, but that does not constitute ALL of his pre-'flight' training. this does however, depend on how he's paying for school. if he got any portion of a GI bill, for example, and is using that, then the 1:1 does not apply. (graduate school is usually a 2:1 deal.) Taking the Marine aviation route takes longer than the navy because the Marines train you to lead Marines. aka-- you're an Officer (aka leader) of Marines, who just happens to fly. to answer your question, 'if he does not become a pilot, can he quit', the answer is not usually, especially if he owes for his education.
the harrier is the older jet-- i know of at least one guy on this forum who flies one. it's been a while since he's posted, but he could probably give you some insight.
you said that he was kicked out of the merchant marine academy for his mouth. do you know if there were any other reasons? like unsatisfactory pt, test scores, or something else? if you've ever spoken to anyone who has gone through Marine Boot Camp/ OCS, they will tell you that you learn very quickly when to shut your mouth. Marines also have a way of taking care of their own problems, so if this type of behavior that you've indicated continues at OCS, he won't be there for very long.
if you screw around in a jet, sure, your chances of dying increase. that's common sense. but if you screw around in a car, your chances of dying increase, and your chances of dying out on the open road are much higher than in the wild blue. the training these pilots go through is exhaustive-- you and your sister should understand that. they train every scenario that can possibly happen, and he'll fly more than one type of plane before he even gets to the jet. (and simulators before that.) if he can't hack it, he'll wash out of the program. squeeze, in south texas, is training in the jet right now, so he can tell you for sure. on the other hand, the military is a dangerous business, so your sister needs to be very clear on that too.
time away-- the Marine jet guys that i know who are not assigned to carriers typically deploy once a year, for 6 months at a time. they are based on the east and west coasts, and in hawaii. so if you sister actually marries this guy, he'll be around, gone for 6 months, then involved in the 6 month work up cycle, (where they can go anywhere for a few days to a few weeks at a time to train), and then gone again for 6 months. i'm not married, but i would think that being married to a Marine would be challenging-- pilots can also be assigned to ground duty, and some pilots have actually been on the ground in iraq.
somthing to think about: a lot of guys recommend taking girlfriends to an airshow-- the theory being if she 'gets it', then the couple has a greater chance of making it. has your sister attended anything like this with her boyfriend? does he get it?
