Between the addition of new anti-ship cruise missiles and the delivery of new F-35 jets with Sidekick compatibility, the U.S. Navy is pushing forward to a new standard for the Joint Strike Fighter program that will peak with the rollout of various Block 4 lethality upgrades later this decade.
Both the F-35B and F-35C are entering a new phase of lethality with a number of new sensors and weapons set to be added to the fighter’s growing portfolio in the coming year. Among those new capabilities is the integration of AGM-158 cruise missile family on the F-35B and F-35C, Early Operational Capability (EOC) of GBU-53 Stormbreaker-II glide bombs, and the integration of two additional air-to-air missiles.
Lockheed Martin integrated an AGM-158C LRASM anti-ship missile on the BF-03 F-35B testbed last week, marking the second integration of the LRASM on an F-35 variant, following in the footsteps of the F-35C which completed captive carry tests in September 2024.
Integration of the AGM-158 family will bring a new low-observable standoff weapon system for external carriage on the F-35 extending out to 1,000 miles with Lockheed Martin’s newest AGM-158 variant, the AGM-158XR, which combines elements of the JASSM-ER and LRASM to extend range and provide additional standoff strike capability. The captive carry tests of LRASM underscore a larger effort underway as Lockheed Martin and the F-35 Joint Program Office prepare for full Block 4 capability.
“Integration of the AGM-158 strike systems family delivers increased reach and lethality against heavily protected, strategic targets.”
Jon Hill, Vice President and General Manager, Air Dominance and Strike Weapons at Lockheed Martin Missiles and Fire Control
F-35s in Lot 17, set to begin production in 2025, are receiving critical prerequisites for the program’s major upgrade to the Block 4 standard, ranging from new weapon capability like the AGM-158 family to new exterior coatings designed to reduce maintenance and improve performance.
Block 4, as a whole, is a multi-service modernization effort that includes more than 80 classified and unclassified capabilities delivered incrementally over various production lots. Some components of the Block 4 list began deliveries in 2019, while others are yet to be delivered–and won’t be for some time.
Weapon Integration Efforts
‘Six-in-the-Bay’ is a capability being pursued by the U.S. Marine Corps, U.S. Navy, and U.S. Air Force for their fleets of F-35C and F-35A fighters, adding two additional air-to-air missiles in the internal weapons bay. The capability, according to internal U.S. Navy documentation, was slated for Lot 15 aircraft and beyond. Naval News reached out to U.S. Navy Public Affairs as part of a larger inquiry to the F-35’s current progress.
‘Six-in-the-Bay’ was first referenced in the U.S. Navy’s FY2021 Unfunded Priority List and in the U.S. Marine Corps’ 2022 Aviation Plan. The first glimpse of an F-35 carrying six AMRAAMS, however, came in a 2011 Lockheed Martin promotional video.
Naval News has received confirmation that the U.S. Navy has taken delivery of ‘Six-in-the-Bay’ capable F-35Cs delivered in the previously-held Lot 15 aircraft. Deliveries of these aircraft resumed in July 2024 with 41 aircraft delivered across the Joint Strike Fighter program by the end of fiscal year 2024. As part of those 41 aircraft, several F-35Cs were delivered to the U.S. Navy with necessary weapons bay modifications needed to enable the internal carriage of the two additional air-to-air missiles.
Lockheed Martin’s internally developed Sidekick rack will enable the internal carriage of six AMRAAM-sized missiles for U.S. Navy and U.S. Marine Corps F-35Cs, as well as U.S. Air Force F-35As. The capability is not yet operational in the U.S. Navy according to an F-35 Joint Program Office representative.
Compatibility for long-range strike weapons like the AGM-88G AARGM-ER is also slated for Lot 15 F-35s according to the U.S. Navy, though it is unclear if Lockheed Martin or the U.S. Navy completed–or even started–integration testing. An integration contract for AARGM-ER on all F-35 variants was awarded in June 2024. No media of AARGM-ER integration has been released by Lockheed Martin, the F-35 JPO, or the U.S. Navy.
The GBU-53/B Stormbreaker-II is the closest to Early Operational Capability with expectations of an Early Operational Capability (EOC) declaration by the second quarter of FY2025, coinciding with the release of the 30R08/30P08 software build, according to the Director, Operational Test and Evaluation (DOT&E). Initial testing of SDB-II with the F-35 began in 2023. Naval News previously reported on the upcoming EOC declaration here.
Sensor Integration Efforts
Block 4 will bring a tranche of new sensors to the F-35, including an all-new radar and EOTS suite for improved situational awareness. The sensor side of the F-35 is much more restricted, and many of the new capabilities remain classified. The U.S. Navy and Lockheed Martin have confirmed some of the Block 4 sensor changes in graphics and media releases.
Northrop Grumman’s AN/APG-85 radar, intended only for the United States, will replace the AN/APG-81 in Lot 17 F-35s and beyond, though it is likely that aircraft have already been modified with the APG-85 radar. A pre-solicitation posted in late 2023 revealed that Northrop Grumman was being considered for production lots 6 through 8, totaling 249 radars, with lots 1-5 already awarded for an unknown number of radars.
Advanced EOTS, or A-EOTS, is being offered by Lockheed Martin as part of the greater Block 4 upgrade. According to the company’s website, A-EOTS “incorporates a wide range of enhancements and upgrades, including short-wave infrared, high-definition television, an infrared marker and improved image detector resolution.” RTX’s Next Generation Electro-Optical Distributed Aperture System (EO DAS) also began delivery in 2023 for integration on Lot 15 aircraft in beyond, another enabling component of the larger Block 4 standard.
Electronic warfare suites are the most obscure Block 4 upgrades. BAE Systems’ AN/ASQ-239 electronic protection (EP) and electronic attack (EA) system is the current operating suite on F-35s. The company has developed a next-generation suite, known as “The Block 4 EW system” for integration on Lot 17 and beyond F-35s. Additional EA and EP capabilities are being fielded with the AN/APG-85.
New Stealth Coatings
Noticeable issues in the F-35’s stealth coating first arose during the deployment of VFA-147 onboard USS Carl Vinson (CVN 70) in 2022 when rust-colored grime appeared on the fuselage. Since then, that grime has been visible on several F-35s deployed at-sea.
Several services have been experimenting with mirror-like coatings designed to reduce the corrosion and general degradation of radar absorbent coatings used on stealth fighters. As Naval News understands, the F-35 will receive a new coating developed in the Next Gen 2.0 OML Coating Program, designed to improve both maintainability and survivability. It is currently being tested with Test and Evaluation Squadron 9 (VX-9) and was trialed with VFA-125 onboard USS Abraham Lincoln (CVN 72) in 2023.
Naval News was not able to verify if the new coating was part of a Block 4 requirement or if it was developed independently as part of an emerging need to improve maintainability while at-sea.
Lockheed Martin is set to deliver a record-breaking number of aircraft to the United States and international partners, between 170 and 190, as the company delivers its backlogged inventory of TR-3 equipped fighters alongside newly built Lot 16 and Lot 17 aircraft.
