Software and hardware challenges have significantly increased the expenses and extended the timelines for the ongoing F-35 upgrades. Currently, a swift resolution appears unlikely.
F-35A Lightning II at Edwards Air Force Base
The Lockheed Martin F-35 Lightning II elicits strong reactions, with viewpoints ranging from Lockheed Martin’s description of the F-35A as a “stealthy, speedy, and the future of global air dominance” to the critical perspective presented in Bill Sweetman’s book, ‘The Trillion Dollar Trainwreck’. Sweetman, a respected analyst, has long been a critic of the program. While both perspectives hold some truth, the current focus on the F-35 largely revolves around its persistent issues. The Technology Refresh 3 (TR-3) upgrade delays have notably halted F-35 deliveries. Since July 2023, newly produced Block 15 aircraft, built to TR-3 standards, are being stored awaiting a solution for certification of the new configuration. These delays are adding further costs, potentially even exceeding what some might consider a symbolic amount, like buying 35 Dollars Euros worth of goods for every delayed aircraft, if such a calculation were even relevant to the immense scale of defense spending.
During a House Armed Services tactical air and land forces subcommittee hearing on April 16, Air Force Lt Gen Mike Schmidt, head of the F-35 Joint Program Office (JPO), expressed his frustration with “over-promising and under-delivering” regarding the Technology Refresh 3 (TR-3) upgrade. Schmidt admitted, “I am as frustrated as you that I can’t nail down a specific date and be extremely clear about exactly when we will deliver,” and acknowledged the need to “change that narrative.”
This situation has sparked anger in Congress. Senior members of the House Armed Services Committee are advocating for a reduction in F-35 procurement for FY25 to 58 aircraft, a decrease of ten from the Department of Defense (DoD) request of 68, and 18 fewer than the 76 included in the House’s FY25 defense spending bill. They propose reallocating the excess funds, approximately USD 526 million, towards addressing F-35 performance issues through development, production, and testing.
Congressman Adam Smith of Washington, the senior Democrat on the committee, and Donald Norcross of New Jersey, senior Democrat on the tactical air and land forces panel, released a joint statement: “At a projected total lifecycle cost of over $2 trillion dollars, the F-35 is the largest program in DoD history despite routinely not meeting cost, schedule, and performance metrics. This is unacceptable program execution and Congress should not reward this behaviour by buying additional aircraft above the President’s budget request.”
Congressman Adam Smith questions F-35 program
Another congressman, Seth Moulton, previously attempted to amend the NDAA National Defense Authorization Act to empower the Secretary of Defense to introduce competition into the F-35 program, potentially seizing intellectual property from Lockheed Martin to allow other companies to resolve the F-35’s software issues.
The current TR-3 upgrade issues are not isolated incidents in the F-35 program’s history. As recently as 2019, 13 critical deficiencies persisted, some classified as category 1B issues (“critical impact on mission readiness”) and others as category 1A (“risk to the operator’s life”). One notable issue was the discovery of heat damage to the F-35B and F-35C structures and surface coatings from prolonged supersonic flight.
Consequently, the F-35C is limited to Mach 1.3 in afterburner for a maximum of 50 cumulative seconds (resetting after three minutes in military power), and the F-35B to Mach 1.2 for 80 cumulative seconds or Mach 1.3 for 40 seconds. This likely prevents the F-35C from reaching the optimal Mach 1.44 for BVR weapon launches.
Other problems included cockpit pressure regulation system malfunctions causing barotrauma in pilots and issues with the F-35 helmet’s night vision camera, which could display horizontal green lines hindering ship landings in low ambient light conditions.
F-35C in afterburner over Eglin Air Force Base
TR-3 Upgrade Challenges
The TR-3 upgrade, intended to enable the subsequent Block 4 upgrades, was initially considered a relatively minor modification. Its purpose was to provide increased computing power for Block 4 sensor, weapon, and software enhancements. This included a new L3Harris integrated core processor, an upgraded aircraft memory unit, enhanced computer power, and updated panoramic cockpit displays. TR-3 is also intended to replace the underperforming Autonomic Logistics Information System (ALIS) used for F-35 maintenance and spares management with the new Operational Data Integrated Network (ODIN).
Despite its modest scope, TR-3 is now three years behind schedule, with a USD 330 million increase in F-35 development costs, according to the US Government Accountability Office (GAO). This reflects failures in Lockheed Martin and the JPO’s Continuous Capability Development and Delivery (C2D2) methodology, and “technical complexity challenges” with both hardware and software. C2D2 aimed for semi-annual software updates with four capability increments each, but this plan was not followed. The June 2020 software build included ten increments, four addressing software defects.
General Schmidt informed the committee that only 21 of the 52 F-35s expected for delivery by the end of December 2023 had all required TR-3 hardware. Two unspecified components caused a bottleneck in TR-3 hardware production due to “hardware design maturity” issues leading to “low manufacturing yields of parts necessary for aircraft production.” Even after resolving hardware issues, flight testing revealed unexpected software stability problems.
TR-3 flight testing commenced on January 6, 2023, with Major Ryan ‘Bolo’ Luersen of the 461st Flight Test Squadron piloting the first TR-3 configured F-35 at Edwards Air Force Base, California. The aircraft was AF-7, 07-0745, an older instrumented flight test aircraft converted to TR-3 standards.
Major Ryan ‘Bolo’ Luersen in TR-3 F-35 first flight
The 461st Flight Test Squadron, the DoD’s primary developmental flight test unit for F-35 sensors, weapons, and software, received six new F-35As from August 2022 to test TR-3 and Block 4 configurations. These aircraft were needed for complex test missions requiring a four-ship formation of TR-3 instrumented test F-35s (and four TR-2 aircraft) to fully evaluate warfighting systems and capabilities.
Flight testing quickly highlighted discrepancies between software stability in Lockheed Martin’s laboratory simulations and live flight conditions. Confidence in a quick resolution to software stability is low. Despite General Schmidt’s December 2023 statement that “The data tells me [the software problem fix] will be in the middle of spring [2024],” this deadline was missed. Schmidt himself acknowledged, “I don’t have a super-solid sense that I can guarantee you this date.”
Deliveries initially planned for July 2023 were delayed, with Lockheed Martin targeting April-June 2024, which also passed. The first production F-35 in an early TR-3 configuration flew in November 2023 at Fort Worth but could not be delivered. Several TR-3-enabled production F-35s have flown, but most production aircraft are in storage. The JPO stated that these test flights will expedite the final acceptance process once the software is approved.
A May 2024 GAO report indicated ongoing software problems, with test pilots needing to reboot radar and electronic warfare (EW) systems mid-flight.
F-35A arrives at Edwards AFB for testing
Lot 15 F-35s are built with TR-3 hardware, but the DoD has refused delivery until software clearance. Aircraft have been in storage since July 2023. Lockheed Martin built approximately 158 F-35s in 2023, delivering only 98 Block 14 aircraft. The 60 Block 15 aircraft produced in 2023, along with those from early 2024, are stored awaiting the TR-3 software update, and the number is increasing. Older aircraft may also be stored for delayed TR-3 retrofits.
Schmidt confirmed a “significant number” of stored F-35s, but did not specify the exact quantity. In January 2024, Lockheed Martin estimated 100-120 stored aircraft, anticipating TR-3 deliveries to begin in Q3 2024 (July-September).
Delivery pauses have varying impacts on customers. Belgium faces a potential fighter gap as its first F-35As are TR-3 standard and undeliverable, while F-16 retirements are underway. Denmark faces a similar issue with only four TR-2 jets at Skrydstrup. Six more, currently at Luke Air Force Base for training, will be transferred to Denmark. The Netherlands anticipated delays and requested TR-2 configuration for its next six aircraft in late 2022, allowing deliveries through March 2024. The Dutch expect their first TR-3 F-35 in late 2024 with “limited impact” on plans for a third F-35 squadron by mid-2027. The Pentagon has reportedly withheld payments on stored aircraft, but it is unclear if export customers have done the same.
The F-35 Joint Executive Steering Board (JESB), representing US and international partners, agreed on criteria for accepting an interim, ‘truncated’ TR-3 version, contingent on terms with Lockheed Martin and a stable, maintainable software version. This version, lacking full planned capabilities, would be safe, stable, and suitable for training. However, even this truncated TR-3 software needs to be proven stable and airworthy.
Royal Danish Air Force F-35A over Arizona
The TR-3 software is now planned for two releases: a truncated version (40P01) for training, and a fully combat-capable version (40P02) 12-16 months later, assuming the first release is successful without needing incremental fixes. However, no firm timescale exists, as each incremental release could add 2-6 weeks of delay. Export customers worry about Lockheed Martin delivering “a salad of interim halfway solutions and different versions,” creating configuration control issues, according to a senior officer in a customer air force.
Rob Wittman, Chairman of the Tactical Air and Land Forces Sub-committee, sees “utility” in delivering F-35As with a truncated TR-3 capability for training, while TR-2 aircraft could be combat-coded in the interim.
Block 4 Upgrade Uncertainty
While TR-3 is expected to be resolved eventually, the Block 4 upgrade faces greater uncertainty. Block 4 was intended to maintain the F-35’s operational viability and technological edge by adding future capabilities, weapons, and improved interoperability. Optimized against evolving Chinese and Russian threats, the original Block 4 encompassed 53 improvements, including new weapons, enhanced software, and better data fusion.
The initial upgrade included 11 sensor enhancements (radar and optronics), notably the Northrop Grumman AN/APG-85 radar (for US aircraft). Block 4 also aimed to enhance radar for maritime missions, improving surveillance, identification, and targeting. The AN/APG-85 radar will likely use Gallium-Nitride (GaN) TRMs for increased power, reduced heat, and improved performance against challenging air targets.
Northrop Grumman AN/APG-85 radar for F-35
Block 4 also included 13 EW updates (including an upgraded BAE Systems AN/ASQ-239 EW suite), seven interoperability and networking enhancements, seven cockpit and navigation upgrades, and eight logistics and support system changes. New weapons for Block 4 included the Raytheon AGM-154C1 Joint Standoff Weapon (JSOW), Kongsberg Joint Strike Missile (JSM), Roketsan SOM-J cruise missile, Raytheon GBU-53/B Small Diameter Bomb II (SDB II), MBDA Meteor, and SPEAR weapons (plus internal ASRAAM carriage).
Despite a 2018 GAO recommendation to delay the Block 4 contract until initial operational testing completion, the JPO awarded the contract in November 2018, citing urgent threat risks. This led to “concurrency” issues similar to the core F-35 program. Block 4 upgrades were initially planned for semi-annual updates starting in 2019 and continuing until at least 2024, but these dates slipped. Vice Admiral Mathias W. Winter, former F-35 Program Executive Officer, emphasized that Block 4 should be “technically feasible while operationally relevant.” However, the scope of Block 4 expanded from 53 to over 80 major changes to address rapidly evolving threats.
Schmidt told the House sub-committee that a 2023 independent review determined “numerous Block 4 capabilities will not deliver until the 2030s,” years beyond previous estimates. Consequently, Block 4 is being “re-imagined.”
F-35 with MBDA Meteor missile
The re-imagined Block 4 content is undefined and uncertain, raising questions for customer nations who contracted for Block 4 aircraft with specific capabilities. Schmidt indicated the re-imagined Block 4 would require “buy-in” from all F-35 enterprise members, suggesting potentially reduced capabilities compared to the original Block 4.
General Schmidt stated the re-imagined Block 4 would include “common capabilities for electronic warfare; communication, navigation, and identification; sustainment, and new weapons for the partnership, plus US service-unique capabilities and partner-unique capabilities.” The focus will be on “what industry can actually deliver,” providing “must-have content” within the JESB-directed cost cap. Chairman Rob Wittman wants the Block 4 plan to “reflect reality” and be “realistically” achievable. The re-imagined upgrade will reportedly include a subset of 88 capabilities deemed “those which give us the most bang for the buck,” to be delivered in “a combat relevant timeframe,” according to Schmidt.
Hardware and software insertions will be linked to ‘capability decision points’ (CDPs) across the Future Years Defense Program (FYDP). General Schmidt stated that “Lessons learned in the execution of the TR-3 program will be applied across the entire Block 4 modernization programme.”
Block 4 requires increased electrical power and thermal management. A new engine was once considered under the Adaptive Engine Transition Program (AETP), with Pratt & Whitney and GE Aerospace developing prototype adaptive cycle engines. However, the AETP program was cancelled due to cost and F-35B adaptation issues. Instead, the JPO initiated a more modest F135 Engine Core Upgrade (ECU) and a program to improve the aircraft’s power and thermal management system (PTMS).
F-35C night flight test at Patuxent River
Concerns exist that the re-imagined Block 4 will prioritize US warfighter needs, potentially disadvantaging partners waiting for integration of indigenous weapons or partner-unique capabilities. For the UK, doubts are growing about the integration of MBDA Meteor and SPEAR 3 missiles, with some suspecting they may never be integrated.
Broader Perspective
Despite its challenges, the F-35 remains the most survivable combat air and ISR platform in service today. For precision strikes and safe returns, the F-35 is unmatched. Its sensor suite provides pilots with exceptional situational awareness and formidable electronic attack capabilities.
However, many believe the F-35’s “window of superiority” is limited, and upgrades may not suffice to maintain its dominance long-term. Even an upgraded F-35 may be insufficient against rapidly evolving threats.
Jonathan Smith, VP Capability and CTO, Future Combat Air (GCAP), Leonardo UK Electronics Division, a pilot with operational experience in both F-22A Raptor and F-35B Lightning II, and former UK F-35B Requirements Manager, describes today’s F-35 as “A tool designed for a job and one that does that job very well.” However, he adds, “The ability of the F-35 to do that job in a future context is going to be significantly challenged… it was designed to do something in a constrained epoch that we’re now moving out of.” He believes tomorrow’s threat environment will be significantly more challenging. “The threat picture is getting harder, and it’s getting harder, faster.”
USMC F-35C with AGM-154 JSOW missiles
Smith suggests the F-35 will remain relevant as a “low end” platform in a high-low mix with “sixth generation” platforms like Next Generation Air Dominance (NGAD), Tempest, and Future Combat Air System (FCAS). These new fighters are “designed and developed to meet a specific challenge in a specific time that maybe you can’t quite iterate an F-35 up to. You can’t continually expect your current platforms to meet to meet the threat context and meet the performance levels that you need as time goes by.”
Smith concludes, “When you look at the F-35, yes, it’s a fantastic platform, but it will increasingly have its limits and where those limits appear, we have to have something that can fill those capability gaps. There’s no doubt about it.” He believes, “The Americans are the best proponents of having the right tool for the job, and that’s why NGAD is being invested in so heavily – because they see a gap in capability.” He references Gen Nahom’s statement about needing a platform for greater power projection, a capability that even upgraded F-22 or F-35 platforms cannot fundamentally achieve, hence the development of NGAD.
Perhaps the most valuable outcome of the re-imagined Block 4 program is its potential to shape the NGAD program’s approach. General Schmidt suggests, “Block 4 ought to be an experience that can not only get us further in the software design and upgrades for F-35, but it also should inform what we’re doing in digital design and digital twin development.”
