Lockheed Martin has demonstrated a dedicated data link between two of its Legion infrared sensor pods, letting a pair of F-16 fighters share targeting information in flight without either aircraft switching on a radar. The test, announced September 16, 2026, took place at Morris Air National Guard Base in Tucson, Arizona, in cooperation with the Air National Guard and the Air Force Reserve Test Center. It marks a step toward a genuinely networked passive sensing capability for fourth-generation fighters operating in the kind of contested, radar-denied airspace that has become the default planning assumption for near-peer conflict.
What Happened in Tucson
The flight tests paired two F-16 Fighting Falcons, each carrying a Legion sensor pod fitted with a pre-production version of HiveLink, a data link built by L3Harris. During the flights, the two pods connected through HiveLink and exchanged sensor data in near real time, and Lockheed Martin says the shared information measurably improved the accuracy of both aircraft’s target tracks. Because each Legion pod observes a target from a slightly different angle, combining their infrared bearings lets the system calculate range to multiple airborne targets almost instantly, a capability the company describes as giving aircrew a form of rapid depth perception for sorting which contacts actually matter in a crowded sky.
Cristin Stengel, programme director for Lockheed Martin Legion, framed the result as the culmination of years of underlying sensor development reaching an operational networking milestone. “Working side by side with the Air National Guard and AATC, we are turning proven infrared search-and-track into a networked, passive capability that is ready now,” Stengel said. “With Legion’s pod-to-pod data link and open architecture, we’re providing aircrews faster, more accurate targeting in the most contested airspaces.”
What Legion Actually Is
Legion, previously known as IRST21, is a passive infrared search-and-track (IRST) sensor. Rather than sending out radar energy and listening for a reflection the way conventional fire-control radar does, an IRST system simply looks for heat, detecting the infrared signature a target aircraft radiates and using that signal alone to detect, track, and range it. That passive approach means a Legion-equipped fighter can build a precise track on another aircraft without ever revealing its own presence through a radar emission an adversary’s warning receiver could pick up, a meaningful survivability advantage in an environment saturated with sophisticated electronic warfare.
Legion is built around a modular open systems architecture, meaning new capabilities, a data link like HiveLink, for instance, can be integrated into the pod without redesigning the underlying sensor. It is already in production and fielded in a podded configuration on U.S. Air Force F-15 and F-16 aircraft, and Lockheed Martin says its transportable design will extend to additional fighter, non-fighter, and uncrewed platforms as the programme matures. The system traces its lineage to Lockheed Martin’s earlier IRST technology, which accumulated more than 300,000 flight hours flying on F-14 and international F-15 aircraft before IRST21 itself was developed as the next generation of that legacy sensor, originally selected to equip the Navy’s F/A-18E/F Super Hornet fleet.
Why Infrared Finds What Radar Cannot
The physical logic behind IRST is worth spelling out, because it explains why passive infrared sensing has become such a persistent thread in modern fighter design even as radar technology has advanced. A stealth aircraft’s entire design exists to minimize its radar cross-section, and a well-optimized low-observable airframe can present a radar return smaller than a marble. Heat is a different story entirely. Supersonic flight generates substantial aerodynamic friction, and a jet engine’s exhaust plume radiates infrared energy regardless of how carefully an airframe’s shape has been sculpted to defeat radar. Against the cold background of the upper atmosphere, that thermal signature can stand out clearly to a sensor built to look for exactly that contrast, even when the same aircraft is nearly invisible to a fire-control radar searching the same patch of sky.
That vulnerability is not a new discovery. IRST technology dates to the 1970s, and Soviet fighters including the MiG-23 and Su-15 carried infrared sensors well before the type most associated with the concept, the MiG-29, entered service in 1983, with the broader Su-27 Flanker family carrying a passive infrared sensor as standard equipment ever since. The United States has moved to close a similar gap across its own fighter fleet, integrating IRST systems on the F-15, F-16, and F-22, while the F-35 carries its own dedicated implementation, the AN/AAQ-37 Distributed Aperture System, six infrared sensors providing full spherical coverage that doubles as both an IRST and a missile approach warning system. Future Military Technologies has covered a parallel effort to unmask stealth aircraft using ultra-wideband photonic radar, a technology that attacks the same fundamental problem through an entirely different physical principle, sweeping across a far wider slice of the radio spectrum than conventional radar can generate rather than avoiding active emission altogether. Between the two approaches, passive infrared sensing that never reveals its own presence and active photonic radar wide enough to see past a stealth coating’s design assumptions, low-observable aircraft are finding fewer places left to hide.
HiveLink Makes the Pods Talk
The networking layer that made the Tucson demonstration possible comes from L3Harris. HiveLink is built to provide resilient connectivity for contested and denied environments, both within line of sight and beyond it, combining mesh networking with Common Data Link (CDL) interoperability and flexible, exportable waveform support. That combination matters for two practical reasons. Mesh networking means data can continue moving through the formation even if a direct link between any two specific aircraft is degraded, since other nodes in the network can relay the information instead. CDL interoperability means HiveLink can exchange data with the wider family of systems already built around that established military data link standard, rather than existing as an isolated, closed system only Legion pods can use. L3Harris has also designed HiveLink to operate on platforms with strict size, weight, and power constraints, the same SWaP discipline Future Military Technologies has examined in the context of ruggedized mission computing for small, endurance-limited platforms, a requirement that matters enormously if HiveLink is eventually meant to fit inside pods carried by aircraft with far less spare payload capacity than an F-16.
Building on a Proven Concept
The pod-to-pod concept itself is not brand new. In April 2022, Eglin Air Force Base’s Integrated Test Team conducted what was described at the time as the first multi-platform operational test of its kind, using an F-15C and an F-16, both fitted with Legion pods, to passively triangulate a target’s position by combining their two IRST bearings, a proof of concept that the underlying sensor fusion mathematics worked in a real flight environment. What the Tucson tests add on top of that earlier demonstration is a dedicated, purpose-built data link engineered specifically for this mission, rather than relying on more general-purpose networking to move the sensor data between aircraft. That distinction is the difference between proving a concept works and building the actual infrastructure needed to field it reliably at scale, and it is why Lockheed Martin is treating HiveLink’s integration, rather than the underlying triangulation technique, as the news.
What Comes Next
Lockheed Martin is conducting the current flight campaign under contract with the Air National Guard, specifically to validate Legion’s performance, transportability, and interoperability across different aircraft and mission sets. The company has outlined a clear road map beyond this milestone, with future work set to integrate software-defined radios and multi-waveform gateways alongside the existing HiveLink connectivity, broadening the range of platforms and networks Legion can plug into. Notably, Lockheed Martin has also flagged eventual support for manned-unmanned teaming, positioning Legion’s networked sensing as a contributor to the same crewed-uncrewed formation concept driving programmes like Anduril’s Thunder autonomous rotorcraft and the U.S. Air Force’s Collaborative Combat Aircraft initiative. A passive, jam-resistant sensor capable of sharing precise target data across a networked formation is exactly the kind of building block that vision depends on, whether the aircraft receiving that data has a pilot in the cockpit or not.
Passive infrared search-and-track
None of the individual pieces demonstrated at Morris Air National Guard Base are entirely new. Passive infrared search-and-track has been finding what radar cannot see since before most of today’s fighter pilots were born, and Legion’s pods have shared triangulated target data before. What the Tucson flight tests actually prove is that Lockheed Martin and L3Harris can now do it through a dedicated, purpose-built link engineered for exactly this job, on hardware already fielded across the F-15 and F-16 fleets, without waiting for a new aircraft programme to carry it. For a fighter force that will be flying fourth-generation airframes alongside newer stealth and uncrewed platforms for decades to come, that kind of low-cost, high-impact upgrade path, wringing a genuinely new networked capability out of jets already sitting on the flight line, may end up mattering more to actual force readiness than any single next-generation programme still years from its first flight.
