Turkey recently won a contract to upgrade three Pakistani Agosta 90B submarines. These subs entered service in 1999, 2003 and 2008. The second two were built in Pakistan with French assistance. Turkey has experience building and upgrading German Type 209 subs and is building some Type 214s for itself as well. Pakistan has also purchased the Type 214.
The Agosta class boats are 1,500 ton (surface displacement) diesel-electric subs with a 36 man crew and four 21 inch torpedo tubes (with 20 torpedoes and/or anti-ship missiles carried.) Pakistan is equipping some of its Agosta 90Bs with an AIP (air independent propulsion) system. This enables the sub to stay under longer, thus making the sub harder to find. AIP allows the sub to travel under water for 4-5 days at low speed (5-10 kilometers an hour).
Pakistan has had good experiences with Turkish firms upgrading Pakistani F-16s. In 2008 Pakistan hired a Turkish firm to upgrade elderly Pakistani F-16s from Block 15 configuration to Block 40 (about halfway to the highest upgrade level for an F-16). The Turks have long had good trade relations with Pakistan, and have also developed, with the help of the U.S. and Israel, a growing aircraft maintenance and upgrade industry. Most of the F-16 work was done in Pakistan, using Turkish engineers and technicians supervising some local workers, and using largely imported (from Turkey and elsewhere) components. As with submarines, Turkey has long maintained one the largest F-16 fleets outside of the United States and learned how to do upgrades with those it owned.