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As the Lockheed Martin F-35 Lightning II is a stealth fighter, it needs to carry its munitions internally in its bays. Having external munitions and fuel tanks significantly increases its radar cross-section and detectability. Its internal bays were designed in the early 2000s, and now they shape engineering decisions when designing next-generation air-to-air missiles and other munitions intended to be used on the platform.
The new AIM-260 Joint Advanced Tactical Missile is one example of a next-generation air-to-air missile designed specifically to fit into the F-35’s bays. While the F-35 can function as a ‘missile truck’ in beast mode, in practice it rarely, if ever, does that. Instead, it outsources that role to other fighter jets (such as the F-15EX and Eurofighter Typhoon). It has what to know about the new four-meter-long missile designed for the F-35.
The Internal Weapons Bay’s Limitations
The F-35 has a major limitation: it needs to carry its weapons internally in order to preserve its stealth profile. This means that missiles need to fit inside its weapons bay, and this is a problem for longer missiles that can’t fit. The F-35’s internal bay is just over four meters long. It is only able to carry around 5,700 lb (2,585 kg) lbs of ordnance internally.
With that being said, the F-35A is able to carry around 22,000 lb (9,980 kg) of munitions externally in ‘Beast Mode‘ bringing the total payload to 27,700 lb (12,565 kg), although this sacrifices stealth. By comparison, the F-15EX Eagle II does not carry munitions internally and carries up to 29,500 lb (13,381 kg) of munitions externally.
In practice, the F-35 rarely flies in beast mode into combat, at least not as far as has been publicly reported. In March 2025, after the type had been in service for around seven years and flown thousands of combat missions, The War Zone reported that Israel had become the first publicly known operator to have used them in beast mode. This was possibly for missions over Gaza or Lebanon, where the F-35 faces no or limited credible threats.
Internal Weapons Bays Are Here To Stay
While the F-35’s internal weapons bays may be seen as a major limitation, they are here to stay. Although they are one of the reasons why the F-35 works well when paired with 4.5-generation fighter jets like the F-15EX (for which the USAF is increasing its order), the Eurofighter Typhoon, and other jets. In RAF service, the F-35s are informally called the ‘assassin,’ while the Eurofighter is dubbed the ‘thug’ by its crews.
The F-35 was not the first fighter jet to have internal bays: those were the F-117 Nighthawk and the F-22 Raptor. As the Raptor is a dedicated air superiority fighter jet, limiting its payload is not as impactful as for aircraft carrying out ground missions. Since then, Russia has developed its Su-57 Felon with internal bays, although it’s unclear if they are operational in mid-2026. South Korea’s KF-21 is being designed with internal bays that will become operational in later block upgrades.
The Chinese J-20 relies on internal weapons bays and has even scrapped the customary internal autocannon. Next-generation prototypes in China (e.g., the J-50 and J-36) also appear to have internal weapons bays. The Anglo-Japanese-Italian GCAP/Tempest fighter has them. Aviation Week, which was allowed to have a sneak peek at the demonstrator under construction, said that:
“The size suggests the demonstrator could carry around twice the internal weapons volume of the F-35’s relatively shallow bays and potentially accommodate larger-diameter stores.”
The Dimensions Of The F-35A’s Bays
However, the US Air Force, Marines, and Navy will have to make do with the F-35’s relatively shallow bays into the 2060s and beyond. The conventional F-35A (used by the Air Force) and carrier-based F-35C (used by the Marines and Navy) share the same internal weapons bay geometry.
The generally accepted dimensions are around 14 feet (4.27 meters) long, 25 inches (0.64 meters) wide, and 25 inches (0.64 meters) deep. The STOVL variant, used by the Marines, is noticeably shorter. It measures around 12.5 to 13 feet long (3.8 to 4.0 meters), making it between six and 12 inches shorter. The width is thought to be slightly less, at around 24 inches (0.61 meters), while the depth is likely around the same, at 25 inches (0.64 meters).
F-35’s internal bay dimensions (per various estimates) | F-35A & F-35C | F-35B |
|---|---|---|
Length | 14 feet (4.27 meters) | 12.5 to 13 feet long (3.8 to 4.0 meters) |
Width | 25 inches (0.64 meters) | 24 inches (0.61 meters) |
Depth | 25 inches (0.64 meters) | 25 inches (0.64 meters) |
In its normal stealth configuration, the F-35A can carry combinations like four AIM-120 AMRAAMs or two 2.000 lb (907 kg) and two AIM-120s or eight GBU-53/B StormBreaker and two to four air-to-air missiles. The latter configuration will be possible after Block 4 upgrades. In the future, it will be able to carry AIM-260 JATMs. The European MBDA Meteor air-to-air missile is also in testing for integration.
The AIM-260 Joint Advanced Tactical Missile
The four-meter missile referenced in the title of this article is the AIM-260 Joint Advanced Tactical Missile. It has been designed specifically to fit in the F-35’s bays, although it may not fit in the F-35B variant’s bays. The missile is a US-developed, air-launched cruise missile (derived from the Naval Strike Missile).
The War Zone reported that the missile first broke cover in May 2026 on an F/A-18F Super Hornet assigned to the Air Test and Evaluation Squadron 31. Flight testing is known to have started years ago. It is expected to augment and eventually replace the AIM-120 AMRAAM in US service. The publication wrote that “unlike the AIM-120, it has no mid-body control surfaces, or even strakes running along the sides. The JATM’s overall configuration reflects optimization for maximum speed and range.”
The US Navy is developing the AIM-260 in cooperation with the Air Force. The services are known to be nervous that the growing reach of Chinese air-to-air missiles, like the PL-15, is eroding their advantages.
It is reported that the missile is designed to engage targets at ranges of at least 120 miles (200 kilometers) or even further. Alex Hollings from Sandboxx News recently reported that a notice published by the Air Force Lifecycle Management Center reveals the service is seeking to develop an air-to-air missile able to reach targets as far as 1,000 nautical miles away (around 11 times that of the AIM-120).
Meteor Vs AIM-260
The European MBDA Meteor is widely regarded either as the world’s best air-to-air missile, or at least belonging to the top tier of such missiles. With that being said, it is also limited by which aircraft it is integrated into, with integration work still ongoing with the F-35. Comparing the missile with the AIM-260 is tricky, as much more is known about the mature Meteor than the highly classified AIM-260.
With that being said, the AIM-260 is thought to be a little longer (13 feet or 4.0 meters vs 12 feet or 3.66 meters). The Meteor uses a novel solid rocket booster and throttleable ramjet propulsion, allowing it to achieve long ranges. Meanwhile, the AIM-260 is widely believed to use an advanced solid-rocket motor rather than ramjet propulsion, although few official details have been released.
The Meteor has speeds of over Mach 4. The AIM-260 is widely believed to be somewhat faster, with many reports estimating speeds approaching Mach 5. However, the Meteor is officially reported to have a range of over 62 miles (100 kilometers), but it is widely believed to be significantly more than that.
It is important to note when comparing air-to-air missile ranges that they are heavily influenced by factors like how high and fast the fighter jet is flying, how high or low the missile flies, the extent of off-board cueing for the missile, and other factors. Ranges are heavily classified, and companies may not be using the same criteria to measure distance.
How The AIM-260 Is Informed By 2002’s Decisions
Much is yet to be learned about the new AIM-260, including its no-escape zone. For example, the Meteor’s throttleable ramjet allows it to maintain thrust during much of its flight rather than simply coasting after motor burnout. This allows it to preserve an unusually high energy in its final phase of engagement and contributes to one of the largest publicly known no-escape zones. A missile’s no-escape zone is not the same as its range.
Two missiles may have ranges of 150 miles, but the practical no-escape zones may differ starkly. The true range and no-escape zone of the AIM-260 remain to be seen. The AIM-260 does highlight a couple of factors. One is the age-old cat-and-mouse of innovation and counter-innovation and adaptation. China may have designed a long-range missile, but that spurs the US to design an even longer one.
The other factor is how engineering decisions made 25 years ago dictate engineering decisions now and decades into the future. Engineers largely fixed the F-35’s internal bays around 2002: those decisions are now informing missile design. With the US only around a third through its F-35 procurement, it is set to inform missile designs for decades to come.
