The Pentagon’s acquisition chief will not declare full rate production (FRP) for the F-35 Joint Strike Fighter by the end of this year, and a Milestone C decision could instead take place up to 13 months later.

Speaking to reporters Oct. 18 at the Pentagon, Undersecretary of Defense for Acquisition and Sustainment Ellen Lord said the FRP decision could come as late as January 2021, rather than December 2019 as both the department and F-35 contractor Lockheed Martin [LMT] had previously indicated.

The delay is due to issues integrating the F-35 into the Air Force’s Joint Simulation Environment (JSE), she said. The JSE is a scalable, expandable, high fidelity government-owned, non-proprietary modeling and simulation environment meant to conduct testing on fifth-plus generation aircraft and systems accreditable for test as a supplement to open-air testing.

Lord said the F-35 Joint Program Office and her office had signed out a program deviation report earlier this week “that documented expected schedule threshold breach in the Milestone C full rate production decision of up to 13 months,” Lord said. The Joint Program Office did not respond for a request for comment by Defense Daily’s deadline Friday.

“What this is a result of – and I follow this very carefully – is the fact that we are not making any progress on the Joint Simulation Environment,” she noted. Integration of the F-35 into the JSE is a “critical portion” of the Joint Strike Fighter’s initial operation, test and evaluation (IOT&E) phase, she added. first reported in September that the F-35 would not make its target fall 2019 deadline for IOT&E completion due to the issues with integrating the aircraft into the JSE. IOT&E is one of several phases that must be complete before a Pentagon program receives a Milestone C decision.

Together with Robert Behler, the Pentagon’s director of test and evaluation, “We have collectively decided that we need to get the JSE absolutely correct before we proceed,” Lord said.

Meanwhile, the Pentagon continues to move ahead with F-35 deliveries to the U.S. fleet as well as to global partners, and the aircraft are performing “exceptionally well,” Lord said.

“We’re very excited about the progress, so it does not change what we’re doing on the production line, what we’re doing in terms of development or sustainability,” she said.

Lockheed Martin said in a Friday statement that the company is “confident the full F-35 enterprise is prepared for full rate production and ready to meet growing customer demand.”

“As Sec. Lord stated earlier today, the F-35 is performing exceptionally well for our customers and we continue to ramp up production, modernize the aircraft and improve sustainment performance,” said Michael Friedman, company spokesman in an emailed statement. “This year our goal is to deliver 131 aircraft and that is on track to grow to over 140 production aircraft deliveries next year.”

To date, more than 435 F-35s are operating from 19 bases around the globe, according to the company.  Eight countries have F-35s operating from a base on their home soil, seven services have declared initial operating capability and four services have conducted F-35 combat operations.

The Defense Department and Lockheed Martin reached a handshake agreement this past June for Lot 12 that includes $34 billion for F-35 Low Rate Initial Production Lots 12-14, and would include 157 aircraft in Lot 12 and 478 F-35s overall (Defense Daily, June 10). Lord said Friday that more detailed negotiations are ongoing and the agreement has not yet been finalized.