intresting read from an artical dated 1st June 2010
F-35 orders remain a matter of debate, but current plans call for the US and UK to purchase approximately 2,600 aircraft. The US Air Force originally planned for 2,036 F-35A aircraft but reduced its requirement to 1,763 in 1997. This total remains the offical requirement though the Air Force has unofficially indicated its order will be reduced to between 1,000 and 1,300 aircraft. Some number of these may also be F-35B models as the Air Force has expressed a requirement for up to 250 STOVL aircraft for close air support missions. Such a purchase would likely assist in reducing unit cost and improving the stability of the STOVL program, which has often been targeted for possible cancellation.
The US Navy and Marine Corps have also begun closer joint operations of their combat aircraft wings in part to reduce the need for new aircraft. The Marines originally requested 642 F-35B models while the Navy planned for 300 F-35C variants. In 1997, these figures were refined to 609 for the Marines and 480 for the Navy for a total of 1,089 F-35 aircraft. As of 2004, that total had been reduced to 680 aircraft including 350 F-35B variants and 330 F-35C models. The services have yet to determine how those aircraft will be allocated since the Marines may recieve a mixture of both CV and STOVL aircraft.
Likewise, the Royal Navy may split its order between the F-35 STOVL and F-35 CV models since the F-35C models could potentially be operated aboard the UK's large aircraft carriers due to enter service in the 2010s. The total UK order has shrunk from 150 to 138 to 50 aircraft and will now only be purchased for the Royal Navy to operate on a single aircraft carrier. The Royal Air Force has opted to replace the Harrier with Typhoons rather than the F-35.
In addition to US and UK orders, the potential exists for over 2,000 F-35 sales to export customers. The international partners currently involved in the program have so far expressed tentative plans for nearly 600 aircraft. Italy is interested in up to 131 planes (including 22 F-35B models for the Navy), Turkey is considering 116, Australia 100, the Netherlands 85, Canada 60, and Denmark and Norway may buy 48 apiece. None of these countries have officially placed orders so far, but the F-35 program is encouraging international partners to commit to firm orders as soon as possible. Convincing the partners to do so may prove difficult, however, given past development delays that have driven up costs and pushed service entry back from 2011 to 2013. These delays may cause international partners to instead order competing aircraft like the Gripen or Eurofighter Typhoon that are already in production. Norway has already threatened to pull out of the program over workshare concerns, and Israel's involvement was suspended for several months in retaliation for possible technology transfer