The F-35 Joint Strike Fighter, the supposed backbone of the Pentagon's future air arsenal, could need additional years of work and billions of dollars in unplanned fixes, the Air Force and the Government Accountability Office revealed on Tuesday. Congressional testimony by Air Force and Navy leaders, plus a new report by the GAO, heaped bad news on a program that was already almost a decade late, hundreds of billions of dollars over its original budget and vexed by mismanagement, safety woes and rigged test results.

At an estimated $1 trillion to develop, purchase and support through 2050, the Lockheed Martin-built F-35 was already the most expensive conventional weapons program ever even before Tuesday's bulletins. The Air Force, Navy and Marine Corps are counting on buying as many as 2,500 F-35s to replace almost every tactical jet in their current inventories. More than a dozen foreign countries are lined up to acquire the stealthy, single-engine fighter as well.

In its report the GAO reserved its most dire language for the JSF's software, which agency expert Michael Sullivan said is “as complicated as anything on earth.” The new jet needs nearly 10 million lines of on-board code, compared to 5 million for the older F-22 and just 1.5 million for the Navy's F/A-18 Super Hornet. "Software providing essential JSF capability has grown in size and complexity, and is taking longer to complete than expected," the GAO warned.

Software delays plus continuing mechanical and safety problems prompted JSF program chief Adm. David Venlet to back away from a firm schedule for the new fighter's frontline introduction. When the F-35 was conceived in the late 1990s, it was expected to begin flying combat missions as early as 2010. Lately military officials have mentioned 2018 as a likely start date. In his Congressional testimony, Venlet declined to even mention a possible timeframe for the JSF's service entry.

The GAO predicts the JSF's $400-billion combined development and production cost will grow later this year, once the Pentagon computes a new program "baseline" – something it's already done no fewer than five times since 2001. Aside from a 400-plane reduction in 2003, the Pentagon has always opted to increase the program's budget rather than cut production numbers. That's no longer possible, Air Force Secretary Michael Donley told Congress. "To the extent that there continue to be cost growth or challenges ... we'll have to take down the number of aircraft," he said.

Air Combat Command, which oversees most of the Air Force's fighter squadrons, seconded Donley's view. "We cannot simply buy our way out of our problems or shortfalls as we have been able to do in the past," the command stated in a report last week.

If cuts do occur, the U.S. will be in good company. Australia, Canada and Japan have already begun backing away from the troubled JSF as the new plane has gradually exceeded their budgets. For these countries, alternatives include the Super Hornet and an upgraded F-15 from Boeing, Lockheed's new F-16V and the European Typhoon, Rafale and Gripen fighters. But so far the U.S. military prefers the F-35, even if the stealthy jet is more than a decade late, twice as expensive as originally projected and available in fewer numbers. "We will remain committed to the long-term success of the F-35 program," Air Combat Command asserted.