Increased production of Lockheed Martin’s F-35 depends more on how the fighter jet fares in testing than how deeply the Pentagon budget is cut, Deputy Defense Secretary Ashton Carter said in an interview.The principal factor in determining whether to ramp up production of the joint strike fighter in the next couple of years “is less our budget situation than it is the maturity of the program,” Carter said.The comments by Carter, who is preparing to exit as the Pentagon’s No. 2 civilian official Dec. 4, reflect the Defense Department’s effort to shelter the costliest U.S. weapons system from $500 billion in defense cuts over a decade under sequestration.“Nothing’s going to be completely insulated” from budget reductions, Carter said. “But the joint strike fighter program is in a lot better position than it was four years ago.” Carter, who has overseen efforts since 2009 to reduce the program’s costs, was interviewed Tuesday.The price tag for 2,443 aircraft — $391.2 billion — has increased by 68 percent since 2001. This year, lawmakers, the Government Accountability Office and the Pentagon’s test office have said the aircraft is making progress in flight tests and in stabilizing production.“Our industry partners came to understand that the key to the joint strike fighter was control of cost,” Carter said. “That’s what we’ve been working on these last four years.”The Congressional Budget Office said last week in its annual menu of options for reducing the federal deficit that the Pentagon could save up to $48.5 billion in budget authority through 2023 by ending the program at the 150 already on order while continuing to buy Boeing F-18E/F fighters and Lockheed F-16s. The Pentagon’s current plan has it buying about 2,300 F-35s through 2037 in addition to about 150 on order, the agency said.Eight primary international partners have committed to buying the plane, including the United Kingdom, Canada and Australia. The Pentagon’s current budget plan calls for increasing production to 42 fighters in fiscal 2015, which begins Oct. 1, from 29 this year. The rate would increase to 62 in 2016, 76 in 2017 and 100 in 2018, according to internal Pentagon documents.Lockheed said this year that it may add 2,400 jobs in Fort Worth over several years if F-35 production is ramped up. The company has about 10,000 employees tied to the program in Fort Worth among about 14,000 employees at the west-side facility. Carter, 59, was the Pentagon’s top weapons buyer before taking over as deputy secretary in late 2011. He has tackled challenges including equipping U.S. troops in Iraq and Afghanistan with fortified vehicles and other equipment, informed by visits with the troops during eight trips to Afghanistan. This report includes material from the Star-Telegram archives.