Age 30
Dude,
The max age for entering UPT is 30. So technically, you have to be started in UPT before your 31st B-Day.
All is not lost though. I know a few guys that got an age waiver that were 32 and 33, but they were already commissioned navigators on C-130s. I have heard of a few guys getting age waivers that were not prior-enlisted, but I don't know their story.
Heavy units are most likely to give an age waiver from what I've seen. So where there's a will there's a way. Good luck.
Flaco