I’d be very careful about trying the career intermission program. Some others on here have said they intend to try it, but I don’t trust the AF as far as I can throw a rock, so it’s a “hard no” for me. Make sure you fully understand the program/rules/regs thoroughly beforehand.
I do think it’s a valuable program for some, but I don’t believe the intent of it was for people to take a break to gain employment somewhere, then try to hide behind USERRA when they are forced to return to active duty for X years. Could be wrong, but I don’t think that will go over too well with your respective airline employer. I know for myself personally, I wouldn’t risk it as it seems foolish.
As others have said, the “safest” (and easiest) option is probably to find a guard/reserve unit, get on full time orders or an AGR slot to make it to 20.