Have your son wear his uniform when travelling and tell the agent he is going to a new post (i.e. put it in the PNR when talking to reservations on the phone). It seems to me that on flights to military-type destinations, there is always some cadet-looking type seated in First. I think the FAs or gate agents upgrade, space available, thinking they are doing their a patriotic duty/favor or like the added security of a military type sitting next to the cockpit.