Pakistan Air Force :
Primary mission statement of the PAF was given by Muhammad Ali Jinnah, the founder of Pakistan during his address to the passing out cadets of the PAF Academy Risalpur on 13th April, 1948. His statement has been taken as an article of faith by all coming generations of PAF personnel:" A country without a strong Air Force is at the mercy of any aggressor, Pakistan must build up her Air Force as quickly as possible, it must be an efficient Air Force, second to none". But the present scenario has forced and enabled the Force to come up with an improved and up-to-date Mission Statement, "To provide, in Synergy with other Armed Forces, an efficient, assured and cost-effective aerial defence of Pakistan".
Origin (1947 - 1951)
The Royal Pakistan Air Force (RPAF) was formed in 1947 following the Partition of India. The RPAF began with 2,332 personnel, a fleet of 24 Tempest II fighter-bombers, 16 Hawker Typhoon fighters (also called Tempest I), two H.P.57 Halifax bombers, 2 Auster aircraft, twelve T-6G Harvard trainers and ten Tiger Moth biplanes. It also got eight C-47 Dakota cargo planes which it used to transport supplies to soldiers fighting in the 1947 War in Kashmir against India. It started with 7 operational airbases scattered all over the provinces. The prefix Royal was removed when Pakistan gained the status of Republic on 23 March 1956. It has since been called Pakistan Air Force (PAF).
Operating these inherited aircraft was far from ideal in Pakistan's diverse terrains, deserts and mountains; frequent attrition and injuries did not make the situation any better. However, by 1948 the air force acquired better aircraft such as the Hawker Fury fighter-bomber and the Bristol Freighter. These new aircraft gave a much-needed boost to the morale and combat capability of the Pakistan Air Force; 93 Hawker Fury and roughly 50-70 Bristol Freighter aircraft were inducted into the PAF by 1950. The jet age (1951 - 1961) Although the Pakistan Air Force had little funds to use and markets to choose from, it entered the jet age quite early. Initially it had planned to acquire US-built F-94Cs, F-86s, or F-84s and produce its order in Pakistan. However, lack of funds and strong British pressure persuaded the PAF to acquire the British Supermarine Attacker. The first squadron equipped with these aircraft was the Number-11 "Arrow". The Supermarine Attacker had a rather unsatisfactory service in the Pakistan Air Force with frequent attrition and maintenance problems.
In 1957 the Pakistan Air Force received 100 American-built F-86 Sabres under the U.S. aid program. Squadron after squadron in the PAF retired its Hawker Furys and Supermarine Attackers, and replaced them with F-86 jet fighters. In 1957 thirty-six year old Air Marshal Asghar Khan became the Pakistan Air Force's first commander-in-chief; his tenure saw a change of PAF discipline, professionalism and quality which even today leaves its positive mark on the PAF. During his eight-year command the PAF saw modernization and re-equipment programs, as well as stricter and better training.
The new generation (1983 - 1989)
In 1979 the Soviet Union invaded Afghanistan to crush opposition and rebellion in its allied neighbour. The violent Soviet invasion brought hundreds of thousands of Afghan refugees to Pakistan. With the war being critical to Pakistan's national sovereignty and integrity, the PAF once again sought out modernization, including the procurement of new generation fighter aircraft. France offered its new Mirage 2000, while the PAF's senior officers were interested in procuring American F-16 or F-18L fighters. Initially the Americans refused to sell the F-16 or F-18L and instead offered F-20, F-5E/F or A-10 aircraft. Eventually the new Republican administration of Ronald Reagan approved the sale of F-16s to Pakistan, and in 1981 an agreement was made to supply 28 General Dynamics F-16A and 12 F-16B "Fighting Falcon" aircraft to the Pakistan Air Force.
The F-16s would be supplied under the "Peace Gate" Foreign Military Sales Program; the first six were delivered in 1983 under "Peace Gate-I" while the remaining 34 arrived by 1986, under the "Peace Gate-II" program. Between 1986 and 1988 Pakistani F-16s took part in frequent skirmishes with Soviet and Afghan aircraft.
Pakistani F-16s typically carry two all-aspect AIM-9Ls on the wingtip rails, along with a pair of AIM-9Ps on the outermost underwing racks. The F-16s also have an important strike role for which they are fitted with the French-built Thomson-CSF ATLIS laser designation pod and have the capability to deliver Paveway laser-guided bombs. The ATLIS was first fitted to Pakistani F-16s in January 1986, which became the first non-European aircraft to be qualified for the ATLIS pod.
During the late 1980s, the Pakistan Air Force's Air Defence system also underwent modernization, including the induction and integration of new land-based AN/TPS-47 radars and new Crotale Surface-to-air missiles. Attempts to acquire a new AWACS aircraft were also made - with the E-3 Sentry being desired, but the U.S would not sell it and instead offered the E-2 Hawkeye.
In 1988 the Pakistan Air Force sought to replace its F-6s and Mirages by 1997 with the procurement of new aircraft; initially a mix of Mirage 2000 and F-16A/B Block-15OCU were to be acquired alongside 90 or so F-7 (Chinese MiG-21). However in 1988 the death of Zia-ul-Haq and the new government's desire to reduce spending on defence resulted in 71 F-16A/B Block-15OCUs instead. These aircraft were to be delivered by 1997 and a follow-on order of F-16C/D Block-30s was thought likely.
The "lost" decade (1991 - 2001)
From 1990 Pakistan was hit by American military embargoes in response to Pakistan's nuclear weapons development; these embargoes prevented the Pakistan Air Force from acquiring the 71 new-built F-16s from the U.S. After the 1998 nuclear tests and 1999 military coup, Pakistan was hit by further sanctions not only from the U.S but other Western nations as well; it would not be until 2002 when the U.S finally lifted most of the embargoes. During the 1990s the Pakistan Air Force strived for alternative sources for its new generation fighter requirement; the French Dassault Mirage 2000-5 was chosen but was too expensive to obtain.
This forced Pakistan to rely heavily on China for military aircraft. Pakistan and China worked together to develop the K-8 trainer, and continue to cooperate on the JF-17 project which aims to provide both nations with a new-generation fighter. This project is a major joint venture between Pakistan Air Force and China Aero-Technology Import and Export Corporation along with Chengdu Aircraft Industry Corporation (CAC). The research and development cost of this project is between 450 to 500 million US dollars. It is financed up to 50%-59% by the government of Pakistan. Estimated cost per aircraft will be around 20 million US dollars. As of 2005, Pakistan had started manufacturing JF-17s in Kamra and the first delivery of planes is expected to take place in 2007.
A PAF F-16A
A PAF F-7PThe PAF today operates F-16s, F-7PGs, F-7MPs, Mirage-IIIs, and Mirage-Vs, a total of 470 to 520 fighters organized in 22 front-line squadrons. The PAF is upgrading fighter aircraft such as the Mirage ROSE-I that can utilize BVR, and Mirage ROSE-III that can carry out surgical strike missions using long-range glide bombs. Pakistan has also started manufacturing 150 JF-17 Thunder fighters at Pakistan Aeronautical Complex at Kamra. The first squadron is expected to join PAF in 2007.
On April 12, 2006, the Government of Pakistan cleared the purchase of up to 77 F-16 fighter planes from the US, costing $3-3.5 billion. The number was later changed to 44 aircraft with the possibility of inducting other aircraft, such as the Eurofighter Typhoon, in the near future. The Government of Pakistan had also approved the purchase of up to 50 Chinese J-10 fighter aircraft.   According to the Business Recorder, a leading financial newspaper in Pakistan,  Pakistan will be initially buying:
36 J-10 fighters from China.
8 JF-17 pre-production fighters from China.
26 F-16 A/B Block-15OCU (ex-Peace Gate III/IV aircraft) from United States.
18 F-16 C/D Block-52 also from United States, with an option for another 18.
Pakistan will also be buying
300 SD-10 BVR air to air missiles.
500 AIM-120 AMRAAMs.
18 targeting pods.
500 joint direct attack munitions.
The number of F-16s has been increased to around 96 aircraft. Pakistan will be looking for additional F-16 MLU from third parties.
Pakistan Air Force Day
Pakistan Defense Day is celebrated every year on the 6th of September, marking the official beginning of the Indo-Pak war of 1965. Air shows and other programs mark the PAF's role in defending the nation.
The PAF recorded its first kill on 10 April 1959 when an Indian Air Force English Electric Canberra plane allegedly on photo reconnaissance mission over Rawalpindi was shot down.
Indo-Pakistani War of 1965
See the main article: Indo-Pakistani War of 1965.
On 6 September 1965 war broke out between India and Pakistan. The first PAF F-104 kill of an Indian Air Force Mystère IV with one of its Sidewinders came on the afternoon of September 7, making it the first combat kill with a Mach 2-capable aircraft. Pakistan attacked India using F-104, F-86, B-57 and RT-33A. The war lasted for 23 days and although it ended indecisively, both in India and Pakistan it is considered a victory. On September 7, 1965 the PAF claimed a heavy toll on the IAF with Sqn Ldr Muhammad Mahmood Alam in his F-86 Sabre claiming as many as six IAF Hunters. .
The PAF had claimed 104 aircraft destroyed for a loss of 19 aircraft, while India stated a loss of 35 aircraft compared to 76 PAF aircraft destroyed. Independent observers too, do not agree on the actual number of aircraft shot down, with figures ranging from as high as 3:1 in Pakistan's favor to 2:1 in India's favor. Since India had the larger air force by far, while Pakistan had better planes at the time, it is possible that the actual ratio of air-kills was equalized at 1:1.
"By all accounts the courage displayed by the Pakistan Air Force pilots is reminiscent of the bravery of the few young and dedicated pilots who saved this country from Nazi invaders in the critical Battle of Britain during the last war." Patrick Seale, The Observer, London, September 12, 1965.
Many of the independent sources, even one of the India military chiefs at that time admitted the total air superiority achieved by the Pakistani air force with in 3 days of the war.
The Six-Day War
See the main article: Six-Day War.
In between the war of 1965 and the Indo-Pakistani War of 1971, PAF sent its pilots to many Arab nations during the Six-Day War. Pakistani pilots flew in the Air Forces of Jordan, Egypt and Iraq, recording 3 confirmed kills against the Israeli Air Force (including Mirages, Mystères and Vautours) without losing any of their own planes.
Yom Kippur War
See the main article: Yom Kippur War.
During this war the PAF sent 16 pilots to the Middle East in order to support Egypt and Syria but by the time they arrived, Egypt had already been pushed into a ceasefire. Syria remained in a state of war against Israel. Eight (8) PAF pilots started flying out of Syrian Airbases; they formed the A-flight of 67 Squadron at Dumayr Airbase.
The Pakistani pilots flew Syrian Mig-21 aircraft conducting CAP missions for the Syrians. Flt/Lt. A. Sattar Alvi became the first Pakistani pilot, during the Yom Kippur War, to shoot down an Israeli Mirage in air combat. He was honored by the Syrian government. Other aerial encounters involved Israeli F4 Phantoms; Pakistan Air Force did not lose a single pilot or aircraft during this war.
The Pakistani pilots stayed on in Syria until 1976, training Syrian pilots in the art of air warfare.
PAF F-16BSee the main article: Soviet-Afghan War.
The Soviet invasion of Afghanistan in 1979 in support of the pro-Soviet government in Kabul, which was being hard-pressed by Mujahadeen rebel forces, marked the start of a decade-long occupation. Mujahadeen rebels continued to harass the occupying Soviet military force as well as the forces of the Afghan regime that it was supporting. The war soon spilled over into neighboring Pakistan, with a horde of refugees fleeing to camps across the border in an attempt to escape the conflict. In addition, many of the rebels used Pakistan as a sanctuary from which to carry out forays into Afghanistan, and a steady flow of US-supplied arms was carried into Afghanistan from staging areas in Pakistan near the border. This inevitably resulted in border violations by Soviet and Afghan aircraft attempting to interdict these operations. Between May 1986 and November 1988, PAF F-16s have shot down at least eight intruders from Afghanistan. Four of the kills were Afghan Su-22s bombers, three were Afghan transports (two An-26s and one An-24), and one was a Soviet Su-25 bomber. Most of these kills were achieved using the AIM-9 Sidewinder, but a Su-22 was destroyed by cannon fire and the one An-24 crash landed after being forced to land upon interception. At least one F-16 was lost in these battles, in the encounter between F-16s and Soviet MiG-23s on 29 April 1987. PAF claims that it was shot down by friendly fire. Other sources suggest that it might have been hit by a bomb dropped by a MiG or that one of the MiG pilots downed it by cannon fire (the MiGs were not armed with missiles) but did not claim it since there was no permission given to fire. , 
War on Terrorism
Numerous raids were carried out by the PAF during the Waziristan conflict.
PAF currently operates an estimated 530 fighter aircraft. Some 70 of the Mirages have been given ROSE upgrades - allowing them to either perform high-altitude air-superiority missions or specialized surface strike missions. The F-7PGs and F-16s are the PAF's main multirole fighter aircraft - while the F-7P is a limited interceptor/ground-strike aircraft. It is likely however that the PAF will procure another 26 F-16A/Bs to start retiring its F-7Ps.
Source : http://en.wikipedia.org/wiki/Pakistan_Air_Force