WASHINGTON — The US Air Force is concerned that development of follow-on software for the F-35 joint strike fighter could be in peril if the Pentagon is forced to operate under a stop-gap spending measure next year.

Development of the as-yet undefined Block 4 software, which will come online sometime in the 2020s, would feel the impact of a long-term continuing resolution (CR), Maj. Gen. Jeffrey Harrigian, director of the F-35 integration office, told reporters on Monday during the Air Force Association's annual conference.

"There will clearly be an impact if we're in a yearlong CR," Harrigian said. "That will be a long-term issue to both our production and then, as we've thought about it, some of our follow-on development plans will also be impacted."

The CR has often been used as a short-term budget measure to fund the government at the previous year's funding levels when lawmakers cannot reach a budget agreement. But this year, sources tell Defense News that Congress is mulling a full-year CR for the first time, which would cause a ripple effect throughout the Pentagon.

Under a CR, platforms currently in production would be limited to last year's funding levels and last year's quantities. This is a particular problem for the F-35 program at a time when the Pentagon is gearing up to triple production of the fighter jet.

Next year, F-35-maker Lockheed Martin will deliver 43 aircraft to the services. During the three years after that, the Pentagon will ramp up production to more than 120 aircraft each year, Lt. Gen. Chris Bogdan, head of the F-35 joint program office, said earlier this month.

While The Air Force plans to declare initial operating capability with software Block 3i next year, but the aircraft will not have warfighting combat capability until delivery of Block 3F in mid-2017. Block 3F is the final configuration of F-35 software, providing data-link imagery, a full weapons suite and embedded training.

But the Pentagon is already planning an upgraded software capability, dubbed Block 4F. The program office is planning to begin follow-on development of Block 4 in the 2019 time frame, Harrigian said., bBut a yearlong CR could change the game, he said.

The Air Force has a skeleton plan for the new capabilities Block 4 will provide, but right now nothing is set in stone, Harrigian noted. The program office is still working through the cost estimate for each of the upgrades included in the new software, he said.

Block 4 will include upgraded weapons, new sensors, and an advanced electro-optical targeting system, which combines forward-looking infrared and infrared search and track functionality to provide pilots precise targeting capability. The program office is also looking at advanced electronic attack capability for Block 4, Harrigian said.

"As you all know, the threat is not sitting on its hands, they continue to evolve," Harrigian said. "So we need to make sure that, as we look at those specific threats, we are bringing capabilities that keep ourselves ahead of that curve."

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