The Air Force (like the Army) allows straight through training for pathology without a required clinical internship (just like the civilian world). Only the Navy still requires a clinical internship to be completed before entering a pathology residency. Most of the Air Force's staff pathologists actually come out of civilian programs by way of a civilian deferral for residency training (the Air Force only maintains a single active duty pathology residency program at SAMMC that graduates ~3 residents per year--though I know of rare AF pathology residents trained at WRNMMC through the years as WRNMMC is technically a tri-service GME program, but this is a special situation that requires the stars to align and some serious work on the part of the applicant). If you are not granted a civilian deferral and rebuffed by the SAMMC program you will be required to complete a clinical internship before you can apply again.
4th year pathology clerkships are easily obtained through the GME office/medical student coordinator at the individual medical centers. If you want to match to an active duty program your best bet is obviously to rotate at that program early in your 4th year, shine on your rotation (n.b. not being a douche/weirdo is just as important as your medical knowledge and a sincere interest in the specialty), and have an application free of serious blemishes (i.e. board failures, disciplinary actions during medical school, letters of recommendation that sandbag you or are meant for your derm application, etc.) . There are some students who really want a civilian deferral for residency and so play weird games that involve not rotating at the active duty programs and maintaining "radio silence" throughout their 4th year in the hope that the military program(s) will pass on them as an "unknown entity" and they will receive their desired civilian deferral. I don't recommend this course of action, but it's your career.
