The Afghan air force has 7,000 personnel and 90 aircraft with about 70 more on order. The problem is not aircraft but Afghans qualified to operate them. Afghanistan already has hundreds of pilots but not enough to operate some types of aircraft. Thus there are four C-130 transports but only enough qualified Afghans to provide one crew. The U.S. continues to provide training for hundreds of new pilots and maintainers. This is meant to make the Afghan Air Force able to handle all current and on-order aircraft. The problem is the tendency for technical people, like pilots and maintainers, to leave the military for better paying and safer jobs in the civilian sector. Even if you try to enforce service contracts it is common for military personnel to simply desert when they have enough money to pay a people smuggler to get them to another country, preferably in the West. Meanwhile the only option is to hire more expensive foreigners to fly and maintain aircraft. Officially that is not done.