Hello Aspirant,
AFCAT means Air Force Common Division Test.It is organized twice a year by indian air force.It has three branches
1.Flying Branch
2.Ground Duty(Technical) Branch
3.Ground duty (Non-technical)Branch
For flying branch
Candidates should passed with minimum 60 percent mark in Maths and physics at 10+2 level.
Graduation with minimum 3 years degree course in any discipline from recognized university with minimum of 60 percent marks or equivalent.
According to this source,
No You cannot able to apply for flying branch.But You can apply for ground duty branch.You are eligible to apply for Flying and AE branches only of you have taken 10+ 2 route to engineering. It is not available when you went through diploma route.
I will attach official link of AFCAT qualification below please go through it

https://afcat.cdac.in/AFCAT/CareerAsPerQualification.html

Hope this will be useful to you.
Good luck.