Identity crisis

As unmanned aerial vehicles proliferate across the conflict spectrum, identification friend or foe (IFF) solutions needs to be continually refined.

The numbers speak for themselves: As of July 2025, the United States’ Federal Aviation Administration (FAA) said that 822,039 unmanned aerial vehicles (UAVs) were registered with the agency to fly in American skies. Of these registrations, 433,407 were for commercial UAVs and 377,484 for recreational aircraft. Drone Industry Insights, an analytical company, noted that drone flights worldwide increased from 15.5 million in 2023 to 19.5 million in 2024. To put matters into perspective, the Air Transport Action Group, an advocacy organisation, said that 35.3 million scheduled commercial flights took place last year. It is safe to assume that, at some point in the future, the number of UAV flights annually will eclipse their manned counterparts. Current battlefields are already congested with UAVs, which have largely become the signature weapon of the ongoing war in Ukraine. The June 2025 so-called ‘Twelve Day War’ between Israel and the United States on the one side, and the Islamic Republic of Iran on the other, saw significant use of UAVs. Reports note that these aircraft were used to reconnoitre targets, deliver ordnance and operate as one-way attack (OWA) UAVs against specific targets during the conflict.

Looking at Ukraine specifically, the numbers of UAVs which could be flying in that theatre of operations over the coming year alone is eyewatering. A report published by Forbes in March 2025 stated that the Ukrainian government has set a target of 4.5 million UAVs to be built by domestic factories alone by the end of 2025. Thousands of such aircraft may be flying at any one moment above the 1,287 km front separating Ukraine from territories currently occupied by Russia.

Unsurprisingly, as UAVs proliferate so do the counter-unmanned aerial vehicle (C-UAV) systems tasked with detecting, and downing, hostile aircraft. Both Russia and Ukraine are pouring significant effort and resources to developing C-UAV systems. A standard C-UAV tactic is to jam the radio frequency (RF) link which connects the aircraft to its pilot. The pilot sends the aircraft commands across this link, and the aircraft sends back telemetry on its flight and also the information, such as imagery intelligence, it is collecting. A standard failsafe mechanism is that the UAV will land in situ, or return to its point of origin, if the RF link is broken. Thus, a UAV may perform these courses of action if jamming breaks its RF link. Likewise, a UAV may take these precautions if it stops receiving position, navigation and timing (PNT) signals. PNT signals are transmitted by global navigation satellite system (GNSS) constellations. Many UAVs use GNSS PNT signals for navigation. Thus, some C-UAV jamming tactics also target the UAV’s GNSS receiver to prevent the aircraft’s reception of PNT signals. For these reasons, both Ukrainian and Russian engineers are endeavouring to develop approaches to reduce the dependency of their UAVs on RF control and GNSS PNT signals.

Current architectures

The global proliferation of UAVs both on, and off, the battlefield creates unique challenges. Air Traffic Control (ATC) authorities must ensure that UAVs and their manned counterparts can share the skies safely. Militaries must ensure they are able to detect and engage red force UAVs. Meanwhile, they must identify their own unmanned aircraft and ensure these are not engaged by friendly C-UAV systems. Ensuring this is easier said than done: Tactical UAVs, such as the multi-rotor first-person view (FPV) aircraft, are increasingly ubiquitous above the battlefield. Such platforms are often small, making them difficult to see, which in turn makes them difficult to identify. To the untrained eye, many of these aircraft can look the same, if not very similar. Even to the trained eye, a UAV flying at 150 m can be difficult to identify with certainty. Armies may also use a myriad of different types making it hard to discriminate a friendly FPV drone from an enemy aircraft. The Dignitas Ukraine foundation, which supports the Ukrainian military and civil society, has stated that the country’s armed forces currently use 100 different types of FPV UAV.

Airpower began tackling the issue of friendly and hostile aircraft identification during the Second World War. The development of IFF technology occurred alongside the growth of radar, with the two technologies having a symbiotic relationship. Radar’s realisation shortly before that conflict gave air defenders the means to identify a target potentially hundreds of kilometres away from the radar’s antenna: The Royal Air Force’s (RAF) AMES Type-1 Chain Home ground-based air surveillance radars deployed around the UK, could potentially detect an air target at ranges of around 160 km (86 NM). While the radar could detect and track the target, it was unable to provide additional information regarding that target’s identity. The answer was found in the IFF Mk.I/II system which began to be deployed by the RAF from 1939. IFF Mk.1 was the experimental system, with the production version which entered service from late 1940 designated IFF Mk.II.

 

IFF Mk.I used a relatively simple call-and-response system: The Type 1 radar would transmit an RF signal which would progressively lose strength the further it travelled. The signal would hit an air target, losing energy once again and then echo back to the radar’s antenna. The echo would have a comparatively weak strength by the time the outgoing signal completed its round trip. The resulting target would show up as a dot on the radar operator’s display. The IFF Mk.1 would be activated when the aircraft received the incoming Type-1 signal. Once activated, the transponder would transmit an amplified signal on the same frequency as the radar signal it had received. This amplified signal would be received at the Type-1 radar, alongside the echo, resulting in a much stronger dot on the radar operator’s screen, compared to the echo on its own. The radar operator would immediately be able to determine that the target could be assumed as friendly. Conversely, a relatively weak dot could be determined as potentially hostile.

IFF Mk.I used an interrogation-response system that has been the hallmark of IFF systems ever since. An IFF interrogator is often co-located with a ground-based air surveillance or fire control radar antenna. The radar and IFF interrogator antennas rotate at the same time, sweeping the sky. As the radar detects a target, the IFF sends out an interrogation signal. This signal is detected by the IFF transponder triggering an automatic response. The resulting response to the interrogation is received and the target is displayed to the radar operator as friendly. Once again, if no response is received, the target may be presumed hostile.

Today’s IFF systems employ significantly more sophistication than their wartime ancestors. It is imperative that red forces cannot exploit blue force IFF signals to portray their aircraft as friendly when in blue force airspace. For this reason, contemporary IFF systems transmit a coded radio signal as an interrogation which the receiving IFF transponder must be programmed to recognise and to respond to with the correct coded reply. These coded interrogations and responses are kept secret and changed regularly. Security protocols like these minimise the likelihood that they can be exploited by a hostile actor.

For context, Mode-5 is the standard NATO IFF protocol now entering service within the Alliance and with allied countries. The protocol takes the standard civilian Mode-S secondary surveillance radar (SSR) protocol and adapts this to military use; an SSR is like a military IFF system. In fact, their technological developments are closely related. An SSR interrogator is collocated with an ATC primary surveillance radar (PSR). As both the SSR and PSR antennas rotate, the latter detects targets and the SSR transmits an interrogation. The aircraft’s transponder will send back information on the aircraft’s identity, altitude and speed which will be overlaid on the controller’s screen next to the target. Mode-S sees all aircraft using the protocol assigned with a unique digital address which is transmitted as part of the SSR response. Additional information such as its geographical location provided by the aircraft’s GNSS receiver is transmitted alongside speed and altitude details.

 

Surely one solution to the problem of UAV identification is therefore to simply to outfit UAVs with IFF transponders? That way, they could automatically identify themselves to friendly interrogations and hence avoid the attentions of their own side’s air defenders, though such an approach has problems. The author’s own records indicate that an individual IFF Mode-5 transponder for a manned aircraft can cost a minimum of USD 50,000. Small, tactical drones like the FPV systems used en masse in Ukraine are intended, to an extent, to be attritable. Equipping such a UAV which may cost a few hundred or few thousand dollars with an IFF system – that may cost ten or a hundred times that – severely undermines the supposed disposability which is a key asset of these aircraft. A further issue is that the UAV’s power supply may not be adequate to power an IFF transponder alongside the aircraft’s other systems, or that added power requirements would impose a size and weight penalty onto the platform.

Small solutions

So is there no solution available? Not quite. IFF systems for UAVs have been in production for some time. Sagetech and Uavionix are two companies that lead the field in this regard. Both offer systems which boast low size, weight and power (SWaP) consumption, optimising them for UAV use. These devices are relatively small and light; Sagetech’s MX12B IFF transponder weighs 190 g, while Uavionix’ SkyTAK is even lighter, weighing a mere 50 g. As these two companies’ wares illustrate, products are available to greatly assist the UAV IFF challenge.

Nonetheless, as the Ukraine theatre shows, challenges remain in implementing effective IFF solutions across diverse UAV fleets. Ukraine’s Brave1 defence innovation incubator told the author that this challenge is not necessarily technical “but organisational and logistical”. A Brave1 spokesperson continued that the “battlefield is filled with over 500 drone manufacturers and thousands of diverse drone types deployed daily by various military units”. Therefore “devising, implementing, and continuously updating a unified IFF system for so many stakeholders requires immense resources and coordination”.

 

A key role of Brave1 is to identify tactical and operational priorities based on feedback from Ukraine’s armed forces. Once these priorities are identified, Brave1 works to exploit potential technological solutions, assist the research and development of these solutions, and deploy them on the battlefield at pace. While remaining taciturn on the IFF solutions Brave1 is supporting, the spokesperson did say that the organisation has seen “significant progress with promising solutions”.

Going beyond typical drone usage, swarming UAVs present specific IFF challenges: A mass of transponder responses to friendly interrogations concentrated in a relatively small area risks creating an electromagnetic deluge. Brave1 warns that equipping swarming UAVs with IFF systems risks creating “unique and complex challenges”, as each UAV would need its own IFF transponder. Furthermore, requirements like these will multiply “the hardware, power and data management requirements for each aircraft”. As such, the complexity of each individual aircraft in the swarm could grow, as could the costs of outfitting swarming UAVs thus. Any IFF system developed for swarming UAVs “must also facilitate secure communications within the swarm for coordinated identification and decision-making, distinguishing friendly swarm members from potential intruders or rogue elements”. As with all UAV IFF systems, the price tag is an issue for capabilities intended to have a short lifespan: “Swarm drones are often designed to be inexpensive and disposable, making the cost and weight of IFF transponders a critical constraint.” The movement of UAV swarms is an additional problem as they “operate dynamically, changing formation and roles”. This behaviour means that IFF systems need to adapt to these rapid changes while maintaining reliable identification. Moreover, “if one drone in a swarm is compromised, it could potentially compromise the IFF integrity of the entire swarm”. Brave1 is working on IFF solutions for swarming UAVs but declined to share specifics due to classification concerns.

As the wars in Ukraine, Gaza and the Persian Gulf illustrate, UAV IFF technology will need to evolve as these aircraft increasingly proliferate at the tactical level and beyond. Discriminating friendly UAVs from hostile aircraft is crucial given the increasing importance of UAVs to situational awareness and intelligence, surveillance and reconnaissance (ISR) collection, among other roles. As the Brave1 spokesperson noted, the continued development of cost-effective, low-SWaP, secure IFF transponders for UAVs “is a top priority, as they will hold the key to winning or losing future drone-centric conflicts”.

Dr Thomas Withington