WASHINGTON — A bipartisan group of lawmakers is urging the White House to fully fund the F-35 Lightning II program in the coming years.

But Senate appropriators are raising concerns about maintenance challenges facing the advanced fifth-generation fighter, and this week questioned the need to buy more F-35s right now.

In a Wednesday letter to President Biden, 89 lawmakers, including Reps. Marc Veasey, D-Texas, and Mike Turner, R-Ohio, said the United States needs to keep investing in F-35s in the fiscal 2023 Defense Department budget request and the Future Years Defense Plan. Veasey and Turner are co-chairs of the congressional Joint Strike Fighter Caucus.

The Pentagon needs to buy at least 100 F-35s for the U.S. military each year, invest in advanced capabilities to stay ahead of threats from adversaries and provide enough funding to sustain the aircraft for decades, the lawmakers wrote in the letter, though they did not spell out specific funding levels.

“It is disappointing that year after year DoD continues to flat-line F-35 production investments, defer needed readiness funding, and underfund advanced capabilities for this critical fleet,” they wrote.

“The F-35 is also an unrivaled national asset that strengthens national security, enhances global partnerships and powers economic growth across our communities,” the lawmakers added. “As you well know, our adversaries continue to advance surface-to-air missile systems and develop their own stealth fighters at an astonishing pace.”

This is particularly concerning, they said, with Air Force fighters nearing an average age of three decades old and the cost to operate and support older aircraft increasing.

“The U.S. must modernize our fighter inventory to ensure we can sustain a strong national defense and maintain an advantage to counter the pacing threat — China,” they wrote.

The lawmakers pointed to the importance of the F-35 to the nation’s manufacturing base, with more than 1,800 suppliers and 254,000 workers playing some part in the program.

“At a time when our economy has suffered the devastating effects of COVID-19, this program has continued to create jobs, foster workforce development and spur economic opportunity,” the letter said.

The Senate Appropriations Committee on Monday also released its version of the fiscal 2022 defense appropriations bill, which calls for hundreds of millions in additional funding to expand depot activities, add more spare engine power modules and improve sustainment for the Air Force’s F-35s.

But in the explanatory statement accompanying the bill, the committee noted delays in fielding the aircraft and threw cold water on calls for procuring more now.

The committee said the F-35 program has had “significant maintenance challenges primarily resulting from power module failures combined with depot repair capacity issues.” This has the committee worried because it has left the military with fewer F-35s available for operations at a time when fewer new F-35s are being delivered.

The committee called for an additional $175 million to more quickly stand up Air Force depot activities, $175 million for F135 spare engine power modules and another $185 million in operation and maintenance funding for sustainment.

The committee said production delays in the F-35 will cause some aircraft deliveries to fall behind schedule. The F-35 Program Executive Officer is revising the delivery schedule to smooth production through 2025, the committee said in the statement.

But, it said, this will mean delays in the fielding of about 34 F-35s.

Because of that, the committee said that while it’s supported procuring more aircraft in past years, “the committee sees the rebaseline as a necessary adjustment, and believes the fact-of-life realities do not justify supporting additional aircraft at this time.”

Stephen Losey is the air warfare reporter for Defense News. He previously covered leadership and personnel issues at Air Force Times, and the Pentagon, special operations and air warfare at Military.com. He has traveled to the Middle East to cover U.S. Air Force operations.

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