Hello

Indian Air force conducts the AFCAT exam. Yes the diploma holders + engineering graduates are eligible to give AFCAT . The eligibility criteria for the exam is that you must have passed your 10+2 with minimum 60% aggregate in physics and maths also you must have completed your graduation in engineering from recognised university. So in this case only you are eligible. You are diploma holder plus you have completed your engineering graduation so you are eligible for the exam .

Hope this helps

Regards