I'm a medical school faculty member (have been for a long time) - one thing to know is that - as mentioned above - while it's probably easier to get into medical school when you're younger, it's not a "carved in stone" deal requiring a waiver like entry into UPT is. We have plenty of prior military folks come to medical school older than their classmates - some officers (pilots and others), some enlisted who do their tour, then go to college & med school. These days coming to med school later than your peers because you've been in the military really is no big deal. So the path of less resistance might be med school after you are a rated pilot.
There is a saying that it's easier to make a Soldier (Airman, Marine, etc) into a physician than to make a physician into a Soldier. Having trained a whole bunch of physicians and having been in the military and around a whole bunch of military people, I think that's right.
Also, don't think you have to major in biology or chemistry in college to get into med school. You do have to take the basic premed stuff (two semesters of biology, two semesters of physics, two semesters of general chemistry, two semesters of organic chemistry) - but other than that major in whatever you want & will make good grades at. We don't care as long as it's an actual college major and your grades are good. I've worked with two chiefs of surgery who were English majors and docs who were music majors, sociology majors, engineers & math majors. try to rock the MCAT - really high MCAT scores make you stand out in a good way although they won't compensate for bad college grades. And I think those people who tell you that prep courses for the MCAT don't make any difference are full of shit. It's a high stakes exam & I highly recommend serious preparation, usually with a prep course.