WASHINGTON Borne of the last downturn in U.S. military spending in the 1990s, Lockheed Martin Corp's F-35 Joint Strike Fighter was intended as a quick and affordable way for the United States and its allies to replace thousands of aging F-16s and other warplanes while avoiding the pitfalls of earlier programs.
Nearly two decades and a $166 billion jump in projected costs later, the world's largest arms program was poised for a high-profile international debut at two British air shows when the Pratt & Whitney engine on one of the jets broke apart and caught fire during a takeoff from a Florida air base.
The incident has grounded the existing fleet of 97 F-35 jets and triggered a fresh wave of criticism about the costly new warplane, although U.S. and British officials are underscoring their continued commitment to the program, which now has a revised price tag of $398.6 billion.
Following is a list of expected purchases of the F-35, according to data provided by Lockheed, the prime contractor for the program, and defense officials in the United States and other purchasing countries.
Lockheed is developing three models of the plane for the U.S. military and eight partner countries that helped fund the plane's development - Britain, Australia, Italy, Turkey, the Netherlands, Denmark, Norway and Canada.
South Korea, Japan and Israel have also placed orders for the jet.
U.S AIR FORCE
The U.S. Air Force plans to buy a total of 1,763 F-35 conventional landing A-models through 2037.
The Air Force is training F-35 pilots and technicians at Eglin Air Force Base in Florida, and recently began night training flights at the base. More than 100 pilots have been qualified to fly the jet.
The Air Force is also flying jets at bases in Nevada and Arizona.
Current plans call for the U.S. Navy to buy 260 C-model F-35s, which have longer wings and a special tailhook that allows them to land on aircraft carriers. Lockheed and the F-35 program are testing a redesigned tailhook, with at-sea testing due to take place in the fall of 2014.
U.S. MARINE CORPS
The Marine Corps, the smallest of the U.S. military branches, plans to buy 340 F-35 B-models, which can take off from shorter runways and land vertically, and 80 F-35 C-models to replace its current fleet of F/A-18 Hornets, EA-6B Prowlers, and AV-8B Harrier "jump jets."
The Marines have been flying jets at an air base in Arizona, and have said they were on track to start using the F-35Bs by mid-2015.
The Royal Air Force and Royal Navy, which have invested $2 billion to help develop the new warplane, plan to buy a total of 138 F-35 B-models.
Britain has so far committed to buying 48 of the new planes, and is expected to announce plans for the next 14 jets this year. It has already received three jets.
Italy initially planned to buy 131 F-35 fighters, but curtailed its order to 90 jets in 2012. It is slated to buy 60 F-35A models and 30 F-35Bs.
Italy's state-owned defense company Finmeccanica is one of the subcontractors on the project and its Alenia unit will assemble the planes purchased by Italy, the Netherlands and Norway at a large facility in northern Italy.
The Dutch military initially planned to buy 85 F-35As in coming years but announced in September that it would buy just 37 jets for now, and could order more later. It has already received two jets that will be used for training.
Turkey is slated to buy 100 F-35As and has placed a firm order for the first two jets.
Australia is slated to buy 100 F-35As, with the first jet to be delivered later this year. In April, Australia announced plans to buy 58 jets in addition to the 14 already ordered.
Norway plans to buy 52 F-35A fighter jets and has authorized the purchase of 16 jets.
Denmark was slated to buy 30 F-35As, but it has launched a fresh competition that will not be decided until the end of June 2015.
Canada was poised to buy 65 F-35As for C$9 billion but announced in December 2012 that it would evaluate all available options for new fighters. This followed an outcry over the government's decision to buy the F-35 without an open competition.
Israel has ordered 19 F-35 jets and plans to order up to 75 jets in coming years. A second order could come later this year.
Japan announced in December 2011 that it was ordering 42 F-35 A-model jets and may order more in coming years. Japan is also building a final assembly and checkout plant for the jets.
South Korea has confirmed its plans to buy 40 F-35A jets to replacing its aging F-4 jets.
Singapore and Belgium are among other countries that have expressed interest in the Lockheed fighter jet.