Jag read the below article it might just help you a little.
Pakistan has ordered a total of 111 F-16A/B aircraft.
Of these, 71 were embargoed by the US due to Pakistan's nuclear weapons program. Of these 71, 28 were actually built but were flown directly to the AMARC at Davis-Monthan AFB for storage.
Over the years, various plans were conceived for these 28 aircraft:
Pakistan wanted to get the aircraft or their money back; they were offered to various nations, none of which were interested; ultimately, the US Navy and USAF entered them into service as aggressor aircraft.
After Pakistan's help in the war on terror, the US lifted the embargo.
In 2005, Pakistan requested 24 new Block 50/52 F-16C/Ds (with option for as much as 55 aircraft). Ultimately an order for 18 F-16s was placed with an option on another 18.
Peace Gate III
Seven years after the first order, in December of 1988, Pakistan ordered 11 additional F-16A/B Block 15 OCU (Operational Capability Upgrade) aircraft (6 Alpha and 5 Bravo models) under the Peace Gate III program.
These aircraft were purchased as attrition replacements and fully paid for, but are still awaiting delivery in the Arizona Desert. The reason for this is that Pakistan got involved in a controversy with the United States over its suspected nuclear weapons capability. Intelligence information reaching US authorities indicated that Pakistan was actively working on a nuclear bomb, had received a design for a bomb from China, had tested a nuclear trigger and was actively producing weapons-grade uranium. Furthermore, the F-16A's of no 9 and 11 squadrons at Sargodha AB have allegedly been modified to carry and deliver a Pakistani nuclear weapon. In addition, Pakistan has steadfastly refused to sign the Nuclear Non-Proliferation Treaty.
As a result, in accordance to the Pressler amendment to the Foreign Assistance Act, which forbids military aid to any nation possessing a nuclear explosive device, the United States government announced on October 6th, 1990 that it had embargoed further arms deliveries to Pakistan.
The 11 Peace Gate III aircraft were consequently stored at AMARC (Aircraft Maintenance and Regeneration Center) at Davis-Monthan AFB, Arizona, also known as the Boneyard. There, they were put in 'Flyable Hold' for 5 years, during which time 85% of each aircraft's fuel system was preserved with JP-9, and each aircraft had its engine run once every 45 days. This resulted in the curious situation that most of those aircraft now have more engine run time than air time, the latter being only 6 hours. This low air-time figure, plus the fact that these aircraft are the most modern F-16A/B's built, is the main reason why countries interested in second-hand F-16s first look at the Pakistani airframes.
Peace Gate IV
In September of 1989, plans were announced by
Pakistan to acquire 60 more F-16A/B's. A contract was signed in the same year under the Peace Gate IV Foreign Military Sales Programs, for the delivery of 60 F-16s for US $1.4 billion or approximately US $23 million a piece. By March of 1994, 11 of these planes had been built and were directly flown into the Sonoran desert where they joined the 11 Peace Gate III aircraft in storage. A further six aircraft were stored by the end of 1994, so that a total of 17 aircraft (7 F-16A's and 10 F-16B's) of the Peace Gate IV order are now stored. A stop-work order affected the remaining 43 planes of the Peace Gate IV contract.
The Brown amendment later eased the restrictions on weapon exports to Pakistan, but specifically excluded the F-16s from this release.
Pakistan had already paid $685 million on the contract for the first 28 F-16s (11 Peace Gate III and 17 Peace Gate IV), and insisted on either having the planes it ordered delivered or getting its money back.
At the end of 1998, the United States announced it would pay Pakistan $326.9 million in cash and up to $140 million in other compensation to settle the eight-year dispute. The $140 million will include about $60 million in US white wheat that Pakistan will receive during the current US fiscal year, which began on October 1st. The remaining $80 million in compensation will be negotiated by the two sides. The F-16 issue has been a headache for Pakistan, which is grappling to repay millions of dollars on its $32 billion in foreign debt amid a hard currency drought caused by sanctions and the suspension of International Monetary Fund programs.
After the attacks on 9/11 the Pakistani government became a major US ally in the war on terror. It was decided to redeliver those aircraft to Pakistan. Untill now, only half of them has been redelivered, with the remainder still to follow.
Peace Drive
On March 25th, 2005,
the US Government announced that it had agreed to Pakistan's request to sell new F-16s. Initially, Pakistan has requested an additional 24 new Block 50/52 F-16C/Ds (with option for as much as 55 aircraft). Not much details are known at this moment about a possible sale of the aircraft to Pakistan. The deal is expected to be concluded by September or October of 2005. As part of the package, it was also agreed that the current fleet of older A/B models would get the MLU update.
As a sign of good gesture, the US agreed to supply Pakistan with a number of F-16s who where build under the Peace Gate III/IV programs.
Finally, after long series of negotiations, on
September 30th, 2006 the contract was signed between the Pakistani and US government for the acquisition of 18 new F-16C/D block 52 aircraft and an option for another 18 more. In the deal the re-delivery of the 26 remaining Peace Gate III/IV aircraft was also agreed and the upgrade of those aircraft - and the remaining F-16A/B fleet - to MLU standards.
http://www.f-16.net/f-16_users_article14.html
F-16s are BOUGHT!!!! its not aid! indians confuse the F-16s with other things! 
