Think I've posted this before here, but I'm one of those guys who got to go to IOC between TBS and API. It was well worth it, a lot of great training. I was pretty gung ho at the time and was on the fence about dropping my air contract. There were 3 of us who had air contracts at IOC, plus a 4th guy who started with one and dropped it near the end of TBS. This was a function of IOC revolving around platoon level training, and you need a certain amount of bodies to fill out a platoon for it to work. If infantry slots are low for any given TBS class, IOC can fill the platoon from E-company or air contracts waiting for API. Back in the mid-late 80's the backup at API was so bad they actually took several companies of Lts and sent them to IOC, Fort Sill, etc, and they did 18 month fleet tours before API. These days if they did that, that actually would likely include a combat deployment. Not saying it would happen again, but weird things have been done before based on the pipeline.
At this point in my life, I'm really, really, really glad I didn't drop that air contract. The temptation to drop it was all about getting right out to the fleet and leading Marines, and this was back in '97, no combat, I'm sure the temptation is even greater these days. During my first 11 years of active duty, I wrote 1 fitrep. One. Uno. Since joining the reserves and doing a mobilized deployment the past 2 years, I've written probably 30 fitreps. So I'm now the typical reserve Major acting like a ground Lt/Capt leading Marines, writing training plans, etc, etc. And I'm still a FAC, so I still get to break things. So in the end, I get to do both. If you drop your air contract, there is no going back, that's a one way door. Guys who were infantry in the fleet are generally going to be infantry in the reserves. They'll start businesses or be middle managers when they get out. Besides the fact that you are considering giving up the fucking coolest job ever, you have many more options later in life with a resume that says "Naval Aviator" vice "Infantry Officer."