WASHINGTON — As the F-35 program inches its way through operational testing, the number of critical technical deficiencies is slowly dwindling, dropping from 11 critical deficiencies in January to seven in July.

However, the exact nature of these problems will remain unknown to the public, even when the deficiency itself is not classified. The F-35 Joint Program Office declined to characterize the fighter jet’s remaining seven critical deficiencies, but said in a statement that it has identified and tested fixes for each problem.

Details of [deficiencies] — even unclassified [deficiencies] — are not publicly releasable because the information is operationally sensitive, and its release could be detrimental to U.S. and international war fighters operating F-35s worldwide,” said F-35 JPO spokeswoman Laura Seal.

Seal noted that all remaining critical deficiencies are classified as category 1B issues, which represent a “critical impact on mission readiness.” The more serious category 1A problems indicate a risk to the operator’s life.

Lockheed Martin also declined to issue additional details on the deficiencies.

“We track all F-35 deficiency reports. However, not all deficiency reports represent contractual deficiencies, but instead may represent observations or potential product improvements,” the company said in a statement.

In June 2019, Defense News published an investigation into the F-35 that detailed all 13 category 1 deficiencies on the books at the time — the first and only time a full list of F-35 critical deficiencies has been publicly released.

The program office confirmed in April 2020 that the number of critical flaws had dropped to seven, with only three deficiencies remaining from the previously released list of known problems:

  • A technical problem involving the F-35′s cockpit pressure regulation system led to several incidents of extreme sinus pain, or barotrauma. In April 2020, the program office believed it would be able to resolve the problem in 2021 after flight testing the fix.
  • On nights with little ambient light, the night vision camera embedded in the F-35 helmet could display horizontal green lines that could make it more difficult for pilots to land on ships. The JPO had intended to test a software update for the Generation III helmet to assess whether that could correct the issue with the hopes of declaring the deficiency solved in 2021.
  • The F-35′s Northrop Grumman-made AN/APG-81 active electronically scanned array radar meets requirements, but the Navy wants to upgrade the system so that it can scan a wider area while in sea-search mode. In 2020, the program office stated that this issue would remain on the books until 2024, when a software update is made to the aircraft’s avionics equipment.

The JPO declined to comment on whether these specific deficiencies are resolved. However, Seal noted four of the seven critical deficiencies are expected to be fixed by the end of October, and another deficiency is scheduled to be fixed in early 2022 after shipboard tests.

The program has not set timelines for resolving the remaining two deficiencies, which “are in work pending test schedules,” Seal said.

The Government Accountability Office recommended the program fix all of the F-35′s critical deficiencies before the Pentagon approves full-rate production, an action the watchdog said would “reduce the potential for additional concurrency costs stemming from continuing to produce aircraft before testing is complete.”

While the Defense Department has concurred with that recommendation, the timeline for a Milestone C decision — which precedes full-rate production — has faced significant delays.

Operational testing must be complete before the Pentagon can make a Milestone C determination. However, that testing is at a standstill while the program office finishes work on the Joint Simulation Environment, a virtual environment that replicates adversarial threats — including highly realistic versions of enemy aircraft and weaponry — that are too complex to be simulated in live training.

The Defense Department intended to complete F-35 simulator testing in advance of a full-production decision in 2019, but testing officials discovered technical problems with the simulator and have not been able to complete the 64 tests requiring the Joint Simulation Environment.

The program could release an updated simulator test schedule as early as August, the GAO stated in a July 13 report. “Until this happens, the full-rate production date remains undetermined,” the GAO said.

Aside from the major category 1 deficiencies, the program is tracking 850 category 2 deficiencies — minor problems that represent a “possible impediment or constraint to successful mission accomplishment,” Seal said.

Of the 850 minor issues, 165 are classified as “enhancements,” meaning they do not represent a deviation from the program’s requirements like most reported deficiencies. These features are typically seen as proposed future upgrades, Seal said.