WASHINGTON — The Senate wants to spend an additional $1.7 billion to buy 17 more F-35 fighter jets for the military in fiscal 2021.

The Senate Appropriations Committee’s $696 billion defense spending bill, which was released Nov. 10, would add 12 F-35As for the Air Force and five F-35Cs for the Navy and Marine Corps for a total of 96 jets in FY21. That’s five more than House appropriators proposed.

The release of the Senate’s spending proposal paves the way for an eventual deal with the House, which passed its own appropriations bill in July. But no matter which chamber of Congress wins out, the Defense Department will fall short of the 98 F-35s it purchased in FY20, potentially signaling that even Congress has a limit on how far it will go to beef up purchases of the Lockheed Martin-made jet.

In addition, lawmakers want more visibility from the Pentagon about how exactly it’s spending taxpayer funds.

The Pentagon requested a total of 79 F-35s in FY21:

  • 48 F-35A conventional-takeoff-and-landing jets for the Air Force.
  • 10 F-35B short-takeoff-and-vertical-landing variants for the Marine Corps.
  • 21 F-35C carrier variants split between the Navy and the Marine Corps.

“The Committee notes that the Department of Defense continues to request fewer than 60 F-35A variants,” which is the Air Force’s yearly procurement goal, “and that the F–35B procurement profile was reduced to 10 aircraft in the fiscal year 2021 President’s budget request, five fewer than were planned in the fiscal year 2020 President’s budget for fiscal year 2021,” the committee stated in its explanation of why it had chosen to boost funding for the program.

The funding, however, will come with some strings attached. Senate appropriators want quarterly reports on the status of Turkish suppliers in the F-35′s supply chain. Turkey was ejected from the F-35 program in 2019 following its acceptance of the Russian S-400 air defense system, and the Pentagon is in the process of removing Turkish companies from the aircraft’s supply chain.

However, the full transition from Turkish-made components will not occur until around 2023 — a timeline that has frustrated some lawmakers.

The committee also directed the Pentagon’s F-35 program office to provide budgetary information about how Lockheed Martin is compensating the government for spare parts that were not ready on time to be installed on the aircraft. The company in September agreed to invest about $70.6 million to fix problems that the Defense Department said had resulted in increased costs and hours lost.

Despite adding funds to purchase more jets, lawmakers raised a number of concerns about a lack of transparency regarding the finer points of F-35 production, sustainment and modernization.

“The committee continues to support follow-on modernization of the F-35” through the department’s Continuous Capability Development and Delivery strategy, which calls for using agile software development practices to enable incremental updates to the F-35 every quarter, the committee said, though it noted “some concerns over the ability to measure delivered software updates against planned capabilities, the synchronization of capability of fielded aircraft, and the ability to maintain training cycles.”

“However, the committee is deeply concerned with the Department’s approach to budgeting for C2D2 and the lack of detail in the budget justification materials,” the committee added, criticizing the program’s budget documentation for not always providing easy “traceability” among requested, allocated and spent funding.

Senate appropriators also questioned the F-35 program’s strategy of buying components in bulk ahead of need, a practice called “economic order quantity.” Usually, bulk purchases of parts are done in tandem with congressionally approved multiyear contracts, but lawmakers approved EOQ procurement for the F-35 with no multiyear contract in place.

The EOQ buy for F-35 lots purchased from FY18 through FY20 never resulted in the estimated $400 million in savings originally projected, the Senate committee said. And because the Pentagon had decreased the number of F-35s it planned to buy over FY21 through FY23, it is unlikely that the projected savings for that time period also would not be reached.

“Given the lack of savings materialized and continued adjustments to F–35 aircraft quantities year-over-year, the committee questions whether appropriations for EOQ should continue to be provided to the F–35 program,” the committee said. “However, the committee notes that changes to funding, contracting, and acquisition strategies midstream could have detrimental effects on program costs and the supplier base and therefore recommends fully funding the EOQ requested in fiscal year 2021.”