The regulation for the age limit for ANG applicants for pilot training is that you have to not have reached your 30th birthday prior to beginning UPT.
See page 12 here. http://static.e-publishing.af.mil/pr...005.pdf#page10 that follows the USAF UPT age AFI as well.

Because it takes a while to bring you on board, get the training slots, physical, officer school, etc etc., most units require you to be 28 or under to interview. That said, each unit has its own policy, and NGB is currently using 35 as the age for waivers to be issued to (that came from someone at NGB with whom I spoke...haven't seen that in writing anywhere). I also heard (take it with a grain of salt) there are waivers for some people older than that depending on the circumstances (usually prior enlisted from what I've heard). Doesnt hurt to go find your way over to a base and start asking around, but talk to pilots at a unit, not a generic recruiter. That said, I've never heard of a 39 year old going to UPT.