Look at what United States Code says:
TITLE 10, US. Code, Subtitle A, PART I, CHAPTER 13,§ 311
Militia: composition and classes
(a) The militia of the United States consists of all able-bodied males at least 17 years of age and, except as provided in section 313 of title 32, under 45 years of age who are, or who have made a declaration of intention to become, citizens of the United States and of female citizens of the United States who are members of the National Guard.
(b) The classes of the militia are—
(1) the organized militia, which consists of the National Guard and the Naval Militia; and
(2) the unorganized militia, which consists of the members of the militia who are not members of the National Guard or the Naval Militia.
Now, Title 32 § 313 states:
(a) To be eligible for original enlistment in the National Guard, a person must be at least 17 years of age and under 45, or under 64 years of age and a former member of the Regular Army, Regular Navy, Regular Air Force, or Regular Marine Corps. To be eligible for reenlistment, a person must be under 64 years of age.
(b) To be eligible for appointment as an officer of the National Guard, a person must -
(1) be a citizen of the United States; and
(2) be at least 18 years of age and under 64.
Maybe I need to check with other branches USAF is currently not taking former service of all things.
Hey you're an Army recruiter!