July 24 (UPI) -- The F-35 Lightning II is nearing completion of its Systems Development and Demonstration phase as the airframe passes 100,000 hours in flight time, Lockheed Martin announced on Monday.
The F-35 Integrated Test Force teams are expected to complete the SDD portion of the jet program by the end of the year, according to Lockheed's F-35 program general manager Jeff Babione.
"This 100K milestone marks a significant level of maturity for the program and the F-35 weapons system," Babione said in a press release.
"We are well positioned to complete air vehicle full 3F and mission systems software development by the end of 2017."
Lockheed said remaining testing of the systems includes validating 3F software, F-35B ski jump testing and austere site operations, high-speed load testing and weapons accuracy tests.
A Government Accountability Office report issued last April was less optimistic than the F-35 program office about 3F software development timelines. Using historical data of delays over the course of the program, GAO estimates that the Block 3F software package might need until May 2018 to finish SDD, as opposed to the program office's projection of Oct. 2017 to the end of the year. The GAO also projects over a billion dollars in additional development costs due to the delays.
Operational F-35's with the Air Force and Marine Corps are currently using an interim software package that contains 89 percent of necessary code, leaving some aircraft capabilities and systems inoperative or incomplete.
Further complicating the issue are Department of Defense requests for follow-on development of Block 4 software upgrades before 3F is out of development, necessitating upgrades of older airframes before their current software is even complete.
Software and hardware development delays have been a consistent feature of the F-35 program, which at over $400 billion is the most expensive in U.S. defense history. The fighters are expected to go into full-rate production in 2019.