What is the point of "career designation"? How hard is it to get selected as an aviator, and do you get more than one shot at it? I don't like the idea of having to think about more than just my next flight.
How hard is it to get selected as an aviator? I'm not even touching that one.
Manpower decisions are incredibly difficult. The planners make decisions now that affect the force in 10, 15, or 20 years. For example, they'll try to recruit X number of officer candidates to make Y number of captains in 5-8 years to make Z number of majors in 10-13 years, etc, etc. They think they need that many majors in13 years because the Corps is supposed to be at total size N with a certain number of battalions, squadrons, etc. By figuring that certain percentages fail at OCS, flight school, get out after their first committment, etc, they can get a requirement.
You can see that a change in any of these things can throw the whole process down a flight of stairs. Say, for example, instead of 50% of officers getting out after their first hitch, the economy isn't so good, so only 20% get out. That means you've got a few too many captains, which will later cause a trainwreck, because then you'll have ridiculously high number of majors (yes, some will say just one is too many). Waiting for all those extras to fail promotion just prolongs the problem.
So, career designation serves as kind of a safety valve to allow the Marine Corps some flexibility to ditch the excess earlier. It achieves most of the goals of "augmentation" a decade ago. Back then, some commissioning sources got reserve commissions and had to get augmented to stay in. It wasn't fair, because USNA and NROTC got a free pass. This is at least a little more fair in that regard.
Aviators, due to the time and expense spent on them, probably won't have to fear the career des boards that much, unless aviation pipelines are really screwed up. Back in the day, though, some augmentation boards did slaughter aviators.
Just remember, it's not personal, it's business.