Before I reply, I think it will be appropriate to know how the pilot training in PAF takes place. I will quote an old post of mine from another thread which will give you an idea about the stages of the training.
Once a flight cadet completes his Bachelors degree, the real fun begins or for some : The real horror...
First, he/she starts ab-initio training on MFI-17 ( Mushshak) at Primary Flying Training Wing (PFT) and learns the basics of flying...once successfully completed the solo phase, cadets begin with basic and gradually proceed to advance manoeuvres....Lots of attrition takes place at this stage and I would say that more than half of the course/class is dropped out permanently from further flying due to various reasons which could be slow progress / lack of flying aptitude / air-sickness/ or many cant cope with the harsh environments so they just simply give up.....
The ones who qualify PFT, proceed to the Jet world on either T-37 or K-8, know as Basic Flying Training (BFT).....Besides solo stage, cadets learn Instrument flying, Advanced manoeuvres, few combat manoeuvres , High / Low level Navigation , formation and night flying....Again, many are dropped out due to slow progress and attrition continues in each phase of flying...
The lucky ones who survive PFT and BFT get the commission in PAF as an officer in the GD(P) branch and are considered eligible to wear the elite Flying Wing on their uniforms....But their miseries arent over yet and the sword of suspension still hangs over their heads....
PFT and BFT are done at PAF Academy Risalpur...After graduating from academy, now for the young budding officers, their next destination is PAF Mianwali.. They report to FCU - Fighter conversion Unit and fly FT-5 for around six months...Unlike MFI-17 and T-37 that have side by side seats,Ft-5 has tendom seats and much faster than T-37...Here they get a bit of a touch of fighter flying....many battle formations and few fighting manoeuvres are learnt...Again few unlucky ones are dropped out at this stage as well....
Next stop, OCU - Operational Conversion Unit on F-7P....By this time , Boys are becoming Men ....stakes are usually very high in OCUs....and the real fun begins ...One flies a supersonic fighter jet for the first time....officers learn Air to Air/ Air to Ground Gunnery, Air Combat ( 1 V 1 , 1 V 2 , 2V2), Missile firing , various air combat manoeuvres , low level strikes and lots of other fighter flying related stuff....Few drop out here as well and sent either to helicopters or Transport aircrafts...
Pheeeeww....The ones who finally survive the OCU as well...are ready to join the ranks of the fighter squadrons in PAF....they are posted to various bases and continue to polish and hone their fighter flying skills in the squadrons...
So this is how it goes from a civilian guy to a fighter pilot......>>>..Initial selection tests----->>ISSB----->>Medical------->>Final merit at Air HQ----->>Reporting at Academy---->>Military training along with gaining the Bachelors degree---->>PFT --->>BFT----->>Graduation from Academy------>>FCU---->>OCU---->>Fighter Squadron (at last)
Although, its seems a very long, strenuous and a demanding journey all the way but trust me: In the end ITS WORTH IT....
Sir MuradK also replied to your queries, so I will just add few more points..
Unlike many other airforces that segregate the fighter and transport/helicopter pilots at a very early stage, PAF trains everyone to become a Fighter pilot. However barring few exceptions, the unsuccessful ones who are generally dropped from the OCUs or considered unsuitable for fighter flying are either sent to helicopters or to the transport aircrafts.
Until late 80s/early 90s majority of pilots did OCU on F-6. When F-7s arrived, there were parallel OCUs of both F-6 and F-7. And since F-6s phased out, now we have only the F-7 OCUs.
When only F-6 was in OCU, the successful pilots were equally split between A-5 and F-6 squadrons. The choice of aircraft was usually made by the students or depending upon the requirements, the seniors will make the decision. After spending 3 to 4 years in an F-6/A-5/F-7 squadron, pilots are then moved onto either Mirage or F-16. Selection mainly depends upon ones :-
1. Flying performance in various roles.
2. Annual Evaluation reports.
3. Squadron commanders recommendation.
PAF trains every pilot in each role no matter which aircraft one is assigned to. For example, while A-5 pilots extensively fly in the ground attack role, but they also have to fly a good chunk of air combat missions every year. They do fly similar and dissimilar air combat missions a lot. Similarly, while an F-7 pilots basic role is air superiority but they do fly lots of staffing, bombing and strike missions too. Hence when a pilot switches from an A-5 to F-16, its not difficult for him to grasp the air combat role or vice versa.
So presently there are two routes to climb up the ladder:-
1. OCU on F-7---> 2 or 3 years in F-7/A-5 ------> Mirage ( another 2 years)-----> F-16
2. OCU on F-7---> 3 to 4 years in F-7/A-5 ------>straight to F-16
Hopefully once we have JF-17, FC-20 and Block 52s in our inventory and no more F-7/A-5/Mirage, the routes could be:-
1. OCU on JF-17---> 2 or 3 years in JF-17 ------>F-16 MLU ( another 2 years)-----> F-16 Block 52
2. OCU on JF-17---> 2 or 3 years in JF-17 ------>FC-20
3. OCU on JF-17---> 2 or 3 years in JF-17 ------>FC-20( another two years)-----> F-16 Block 52
What I have seen and learnt that IAF also follows a similar pattern. Their base fighter is Mig-21 and from there they move up the ladder to Mig 23/Mig 27/Jaguar----> Mig 29/ Mirage-2000 and then onto SU-30. There can be few variations in this path but this is how it generally works.