You can appear in National Defense Academy (NDA) examination after qualifying 10+2 exam only. 10th passed students are not eligible for NDA examination to join Indian air force ..

Educational Qualifications
For Air Force and Naval Wings of NDA
You have to pass 12th of the 10+2 pattern of school Education with Physics and Mathematics, or equivalent

Age-limits
16-1/2 - 19 Years

Important dates :
NDA & NA Exam 2014
Notification Date : 21st December 2013
Last dates for Applications : 20th January 2014
Examination will be held on : 20th April 2014

N.D.A. & N.A. Exam (ii) 2014
Notification Date : 21st June 2014
Last dates for Applications : 21st July 2014
Examination will be held on : 28th September 2014