The air/air combo is incredibly (and surprisingly) stable. Make sure during the CH j.c dash 6a, when you're inputting j.2c, you're pressing 8 and not 9. lt seems stupid, but i've managed to get it working so much more with 8.
lf they were at max jump height you'll have to delay the dash 6a bit.
lt also works on Lambda, Hazama, and Bang.
Combo is sexy.