Over the last three years, Pakistan's success against the Taliban, along the Afghan border, was partially the result of their using lots of helicopters. Dozens of U.S. AH-1F gunships and even more Russian Mi-17 transports were used heavily. But not so much now. The Pakistanis refuse to move on the last Taliban sanctuary in North Waziristan. The real reason is that they do not want to wipe out the Taliban completely, but the reasons given to nagging Americans are more along the lines of "it's too expensive" or "we're not ready yet". One of the more expensive items is maintaining all those helicopters. The Pakistanis say that, in addition to the expense, the Taliban have scattered, and can't be found, providing no targets for the helicopters. But American UAVs find and attack Taliban and al Qaeda leaders several times a week. The real reason for the Pakistani helicopters staying on the ground is that the money for maintenance has been stolen.
It's happened before. When the Pakistani offensive against the Taliban began three years ago, one of the first things they had to do was halt the theft of the $7 million a month the U.S. was providing for the maintenance of all those helicopters. Along with the money, there were also some American technical experts, to help maintain the helicopters. But for over two years previously, most of that money was stolen by politicians and army commanders, and the helicopters spent much of their time on the ground. But when the order came down to go after the Taliban, the word went out to leave the helicopter maintenance money (or at least most of it) alone so the birds could be made ready to join the fight.
Corruption has long been a major problem in Pakistan. Even in the military, the most disciplined organization in the country, taking a little (or a lot) off the top is an accepted way of doing business. But when there is a major threat, the stealing can stop, or at least abate, for a while.
Every new Pakistani government promises to clean up corruption, but none ever has. Often the new guys will throw some of their predecessors in jail, or even execute a few, but then it's business as usual. The current new government has made more noise about stopping terrorism, so one can assume that the theft will continue.