The US military's F-35A fighter jets opened their internal weapons bays; the "Six in the Bay" upgrade project aims to increase the number of internal missiles from four to six by September 2030. (Photo: US Department of Defense)
[Compiled by Chen Chengliang/Comprehensive Report] The F-35, the main stealth fighter of the US military, will be able to carry more air combat missiles in its internal bomb bay in the future. The latest procurement assessment report of the U.S. military revealed that the U.S. military is promoting a modernization project called "Six in the Bay" (SITB). The goal is to increase the F-35's internal missile carrying capacity from the original 4 to 6 missiles while maintaining the internal storage configuration, increasing the missile carrying capacity by 50%. The development goal is expected to be reached in September 2030.
According to "Army Recognition", this upgrade plan is listed in the US military's "F-35 Modernization Selected Procurement Report for Fiscal Year 2027". In order to maintain stealth performance, the F-35 fighter jet can store weapons in the bomb bay inside the fuselage when performing relevant combat missions. The core of this SITB project is to allow fighter aircraft to carry more internal air combat missiles at one time without adding external weapons.
Please read on...
Through this SITB project, the US military hopes to increase the internal missile carrying capacity of the F-35 from four to six without relying on wing pylons and maintaining a low-detectable configuration. After conversion, the number of internal air combat missiles that a single F-35 can carry will increase by 50%, allowing the fighter to have more available ammunition without adding external weapons.
This design is particularly important for the F-35, because external weapons may increase radar reflection characteristics, while internal weapons help maintain the fighter's original low-detectability configuration. The U.S. Marine Corps' 2026 aviation plan has also listed "six bombs in the cabin" as one of the weapons integration projects of the F-35C.
Why add 2 more pieces? The United States has not announced the modification method yet.
However, the latest official document does not disclose the specific mechanical modification methods of SITB, including how to adjust the weapon rack, how to configure the internal bomb bay, and what models the two additional missiles will use. The document also does not explain which models of F-35A, F-35B, and F-35C this upgrade is applicable to.
The outside world has discussed using "Sidekick" weapons racks to add internally mounted missiles to the F-35 in the past, but there is currently insufficient official information to confirm that SITB is adopting this solution. Therefore, the focus that can be determined at this stage is still “increasing from 4 to 6” and the development goal of September 2030.
The "six bombs in the cabin" is not an independent weapons program, but part of the overall F-35 modernization project. The United States is also promoting the upgrade of sensors, communications, electronic warfare and weapons integration capabilities, and enhancing fighter aircraft performance through Block 4 and related software and hardware updates.
Currently, the US military’s public information confirms the SITB’s ammunition carrying capacity and duration. As for the final internal weapon configuration and the applicable scope of various types of F-35, follow-up testing and certification are still pending.
