U.S. Navy and Air Force Developing Compact Variant of AIM-9X Sidewinder Missile

Development Overview The U.S. Navy and U.S.

Air Force are developing a compact variant of the AIM-9X Sidewinder air-to-air missile. The Navy, which manages the Sidewinder program in cooperation with the Air Force, has requested $83.3 million in its fiscal year 2027 budget for work on this AIM-9X Compact Variant.

The Air Force's proposed fiscal year 2027 budget mentions the project but states it will not contribute funding until fiscal year 2028. Risk reduction efforts for the compact variant began in fiscal year 2025 under the System Improvement Plan IV upgrade program.

The new missile repackages that technology into a smaller airframe designed for internal carriage on advanced aircraft, according to Navy budget documents. It is intended to offer greater standoff range, improved kinematic performance, and increased aircraft weapon station capacity while maintaining inner boundary performance.

In fiscal year 2027, the program plans to advance hardware and software designs, focusing on critical components and compatibility with advanced platforms. This includes platform integration, material and energetics studies, modeling, simulation, analysis, system safety analysis, and risk-reduction testing.

The Navy's budget documents state these efforts will mature the complete system baseline. The compact variant builds on the capabilities of current AIM-9X Block II and Block II+ missiles, which feature imaging infrared guidance, thrust-vectoring, high-off-boresight targeting, and lock-on-after-launch functions.

While specific details on the new variant's configuration, size reduction, or methods for achieving improved range are not provided, the core AIM-9X design measures just under 10 feet long and five inches in diameter, compared to the AIM-120 AMRAAM's 12 feet and seven inches.

The smaller size could allow aircraft to carry more missiles internally, increasing magazine depth without altering loadouts. This is particularly relevant for stealthy aircraft with fixed internal bay dimensions, such as the F-35, where Lockheed Martin has developed the Sidekick capability to increase AIM-120 capacity from four to six in A and C variants.

The compact AIM-9X may also suit collaborative combat aircraft drones, which have limited stores capacity. The Air Force is testing drones like Anduril's YFQ-44A Fury and General Atomics' YFQ-42A Dark Merlin under its CCA program, with Fury seen carrying inert AIM-120s externally.

Other designs include Kratos' XQ-58A, Boeing's MQ-28 Ghost Bat, and Northrop Grumman's YFQ-48A Talon Blue, some with internal bays. The MQ-28, developed for the Royal Australian Air Force, has conducted a live-fire AIM-120 test externally, with future versions planned to include internal bays.