Effective and highly sophisticated, NATO has airborne platforms to keep watch on air and surface activities and ensure the Alliance’s and friendly tri-service forces are fed with the best possible, real-time information to gain and maintain advantage in any complex battlespace.

NATO has several technological heavyweights in its arsenal of airborne sensing capabilities, which, together, support a wide-range of peacetime and wartime activities conducted by the Alliance. This article takes a brief look at some of NATO’s airborne sensing capabilities and force structure, then focuses on two of its key assets: the E3A Sentry AWACS and the RQ-4D Unmanned Aerial Vehicle (UAV) platform.


Under Allied Air Command’s operational control, the NATO Airborne Early Warning and Control Force (NAEW&C Force), the Alliance’s largest multi-national collaborative venture, has its HQ located at NATO Air Base (NAB) Geilenkirchen in Germany. It was here, in 1982, that the first NATO Boeing E-3A Sentry Airborne Warning and Control System (AWACS) aircraft arrived to become the Alliance’s key ‘eye-in-the-sky’ component, providing airspace surveillance, battlespace management, as well as command, control and communications (C3) capabilities to NATO.

These airborne sensing platforms have supported such activities as peacetime air policing, counter-terrorism, evacuation, humanitarian and crisis-response operations, as well as the full spectrum of wartime missions. Today, the AWACS fleet at Geilenkirchen comprises 14 Boeing E-3A Sentry aircraft capable of detecting air and surface contacts over large distances, though as part of a larger AEW and airborne reconnaissance entity. The NAEW&C Force currently comprises two operational units, the first consisting of the 14 NATO-owned E-3A aircraft, manned by international crews from 19 NATO member countries. The other unit is the force’s E-3D component based at RAF Waddington in the UK, currently operating three, RAF-manned, Boeing E-3D aircraft; these are set to be replaced by E-7 Wedgetail AEW&C aircraft in 2024. France, with an NAEW&C Force observer role, participates in joint exercises and ensures its E-3F planes remain interoperable with other E-3 fleets. The NAEW&C Force also maintains three forward-operating bases (FOBs) at Konya in Turkey, Aktion in Greece, and Trapani in Italy, as well as a forward-operating location (FOL) at Ørland, Norway.

NATO’s fleet of AWACS aircraft provide the alliance surveillance, as well as airborne C3 and air battle management capabilities.
Credit: NATO

Also owned and operated by NATO is the Alliance Ground Surveillance (AGS) Force, comprising five NATO RQ-4D unmanned aerial vehicles (UAVs) and associated European-sourced ground command and control stations. The UAVs provide Allied forces with near real-time terrestrial and maritime situational awareness in support of a full range of NATO military, as well as civil-military missions and use advanced radar sensors to continuously detect and track moving objects throughout observed areas, providing radar imagery of areas of interest and stationary objects. Based on the USAF Block 40 Northrop Grumman Global Hawk, the RQ-4D system has been adapted to meet NATO’s specific intelligence-gathering, surveillance and reconnaissance requirements.

The AGS also comes under operational control of Allied Air Command and enables persistent surveillance to be carried out over wide areas from high-altitude, with these long-endurance aircraft capable of operating at considerable stand-off distances in any weather or visibility. The AGS has its main base at the Sigonella Air Base in Italy, which serves as a NATO Joint Intelligence, Surveillance and Reconnaissance deployment base and from where all five RQ-4D aircraft operate. While the majority of the AGS personnel are in Italy, some are based at Allied Command Operations in Mons, Belgium and at HQ Allied Air Command in Ramstein, Germany.

AWACS in Focus

NATO’s fleet of AWACS aircraft provide the Alliance with surveillance, as well as airborne C3 and air battle management capabilities that are immediately available in the skies over Europe. The planes in their Airborne Early Warning and Control role can provide airspace surveillance and early detection of airborne threats, such as enemy aircraft and missiles. Support to maritime operations can also be provided, using its maritime surveillance radar to provide a picture of real-time activities at sea. AWACS aircraft also provide control and management of friendly airspace and aircraft, including the coordination of search and rescue (SAR) operations. Since the E-3A component of the NAEW&C Force was established, it has undergone various modernisation programmes, (more of which later), to upgrade such things as communications, navigation and radar equipment.

Specs and Capabilities

NATO’s E-3A AWACS aircraft is a modified Boeing 707/320 commercial airframe, 46.6 m long, 4.5 m wide, and with a 44.43 m wingspan. They are powered by four TF-33-PW110A turbojet engines and the distinctive rotating radome, (also known as a rotodome), which has a diameter of 9.1 m. The rotodome is 1.8 m thick and is held 3.33 m above the fuselage by two struts. Equipped with long-range radar and passive sensors, AWACS is capable of detecting air and surface contacts at long range; combined with an identification friend or foe (IFF) sub-system, the radar can detect, identify and track enemy and friendly low-flying aircraft by eliminating ground clutter returns.

Information collected by AWACS can be transmitted directly from the aircraft to other users on land, at sea or in the air in near real time. The aircraft typically operate at altitudes of around 10 km (32,808 ft) from which a single E-3A can constantly monitor the airspace within a radius of over 400 km, exchanging information with ground-based, sea-based and airborne commanders via digital data links; three E-3As with overlapping orbits can cover the entire area of Central Europe. Using pulse Doppler radar, and flying within NATO airspace, NATO’s AWACS planes can distinguish between targets and ground reflections to give early warning to friendly land, sea and air forces of low or high-flying aircraft or aerial threats operating from, or over, the territory of a potential, or active, aggressor. Though capable of flying longer operations with in-flight refuelling, AWACS aircraft typically operate for about eight and a half hours and cover surveillance areas of more than 310,798 km², its maximum range under normal circumstances is 9,250 km. The system’s active surveillance radar sub-system is located in the rotodome, which rotates once every 10 seconds and provides 360° radar coverage and surveillance from the Earth’s surface up into the stratosphere, over land or water; it can, for example, detect aircraft at ranges of over 400 km. The aircraft has an integrated command and control battle management, or C2BM, surveillance, target detection, and tracking platform that provides an accurate, real-time picture of the battlespace to the Joint Air Operations Centre.

The E-3A’s major sub-systems include its avionics, navigation, communications, sensors (radar and passive detection) and identification tools (IFF/SIF – selective identification feature). The mission suite includes consoles that display computer-processed data in graphic and tabular format on video screens. Each aircraft is manned by a flight crew of three and mission crew of 12, the latter tailored for each flight to meet the requirements of each assigned mission and performing all surveillance, identification, weapons control, battle management and communications functions.

Radar and computer subsystems on the E-3A Sentry can gather and present a range of battlefield information, such as position and tracking information of enemy aircraft and ships, and location and status of friendly platforms, all to be sent to major command and control centres in rear areas or aboard ships, including real-time information needed for interdiction, reconnaissance, airlift/SAR and close-air support for friendly ground forces. It can also provide information for commanders of air operations to gain and maintain control of the air battle and can direct fighter-interceptor aircraft towards enemy targets detected approaching NATO member country borders.

During hostilities, AWACS intel can also be shared in real time at the highest governmental levels of NATO member countries.

AWACS – Revolving and Evolving

All AWACS aircraft undergo continuous modifications and modernisation. In 2018/2019, for example, major upgrades took place in which a digital, or glass, cockpit and other modifications were completed by Boeing, in part to meet changing European air traffic management requirements. Upgrades included five full-colour digital displays in each aircraft, replacing 1970’s-era dials and providing the crew with customisable engine, navigation and radar data. These digital capabilities have also allowed NATO to consolidate crew responsibilities.

The latest upgrades currently underway are large-scale mission and audio system modernisation efforts, designated the Final Lifetime Extension Programme (FLEP), and intended to ensure the aircraft remain operationally effective through 2035.

The FLEP is valued at USD 1 Bn, (Boeing is prime contractor with several sub-contractors from NATO member defence industries), and will provide AWACS with sophisticated new communications and networking capabilities, including upgrades to data link and voice communications capabilities, and with an enhanced wide-band, beyond-line-of-sight, airborne networking capability. The first AWACS entered the FLEP in April 2022 to provide what Boeing states as ‘critical modifications to improve the system capability, interoperability and availability’ of the aircraft, which Kim Stollar, Boeing MD for Europe & NATO Government Affairs said would support the Alliance’s smooth transition from the AWACS into the Alliance Future Surveillance and Control (AFSC) capability.

The Alliance already raised the subject of an AWACS successor at NATO’s Warsaw conference in 2016 when it was agreed that, “by 2035, the Alliance needs to have a follow-on capability to the E-3 AWACS. Based on high-level military requirements, we have decided to collectively start the process of defining options for future NATO surveillance and control capabilities.” This effort has since been carried forward as the AFSC initiative involving all NATO members. It is evaluating new technologies and a ‘system-of-systems’ approach, that will potentially combine air, ground, space and unmanned systems, networked together, to collect and share battlespace information. A 2018 AFSC first phase led to six concept proposals from trans-Atlantic industry consortia delivered in 2020, with the best innovative ideas selected by NATO for further development. A second phase competition involving those ideas was launched in 2021. Then, in March 2022, a Boeing-led industry team won a NATO E-3 replacement contract from the NATO Support and Procurement Agency (NSPA) to conduct a risk reduction and feasibility study of future air surveillance, command, and control concepts to help NATO refine concepts to replace the capabilities currently provided by its AWACS fleet. The Boeing-led team – the Abiliti partnership – comprises: Indra, Spain; Leonardo, Italy; Thales, France; ESG Elektroniksystem und Logistik, Germany; Lufthansa Technik, Germany; and Mott MacDonald, UK.

AWACS – Latest and Urgent Operations

AWACS aircraft have flown multiple missions over the years, from its ‘Assurance Measures’ missions since 2014 to its eastern allies, following Russia’s illegal annexation of Crimea, to tailored Assurance Measures missions over Turkey, following the crisis in Syria, and operations against ISIS.

The aim of the missions following the Crimea annexation was to demonstrate NATO’s collective resolve, its defensive nature, and to deter Russia from further aggression or the threat of aggression against NATO members! That worked well. It begs the question, what have AWACS been doing since Russia’s 24 February 2022 invasion of Ukraine? Well, in reaction to the build-up of Russian troops at Ukraine’s borders prior to the invasion, the NAEW&C Force began preparations for additional intensive air operations and enhanced vigilance activities to substantially increase Allied readiness. All aircraft were prepared to be ready continuously and since the invasion, flying hours have significantly increased, ensuring the comprehensive monitoring of the evolving situation on NATO’s Eastern flank.

Unsurprisingly, NATO has also considerably increased the number of fighter jets on alert across Eastern Europe in response to Russia’s war against Ukraine. Major General Jörg Lebert, Allied Air Command HQ Chief of Staff, said, “NATO air forces have bolstered their presence in the eastern part of the Alliance helping to shield NATO against any aggression.

Several dozen fighter jets are on alert at any time to respond to possible airspace violations and to deter aggression. Allied Air Command integrates the Allied air forces’ fighters, air-to-air refuelling and transport aircraft, as well as Allied and NATO AWACS platforms into standing arrangements to safeguard allied skies. These assets enable NATO to patrol Allied airspace and have 24/7 situational awareness above NATO and adjacent territory.” A Joint Force Air Component (JFAC) has been stood up at Allied Air Command to plan, task and control Allied aircraft flying these latest Enhanced Vigilance Activities.

Alliance Ground Surveillance

Complementing NATO’s AWACS eyes in the sky is NATO’s Alliance Ground Surveillance (AGS) system, based at the AGS main operating base in Sigonella, Italy, and comprising five NATO RQ-4D Phoenix (Global Hawk) UAV and a series of associated ground command and control stations. The airborne system provides a near-real-time terrestrial and maritime Intelligence, Surveillance and Reconnaissance (ISR) capability for NATO forces and Allies, delivering in-theatre situational awareness to commanders of units on the battlefield. The system’s role extends from the support and protection of Allied ground troops and civilian populations, to border control and maritime safety, counter terrorism activities, crisis management and humanitarian assistance in natural disasters. Like AWACS, AGS assets are NATO-owned and operated and enable the Alliance to perform persistent surveillance over wide areas.

The RQ-4D platform is a high-altitude, long-endurance (HALE) ISR aircraft, which can operate at considerable stand-off distances in all weather and visibility. Its advanced radar sensors continuously detect and track surface moving objects, as well as highlighting stationary targets throughout an observed area of interest. The platform has a wingspan of 39.8 m, is 14.5 m long, and stands 4.7 m high. Weighing 6,781 kg, the Phoenix is powered by a Rolls Royce-North American AE 3007H turbofan engine delivering 33,800 N of thrust.

It has a maximum take-off weight of 14,628 kg and a typical 1,360 kg payload. With a fuel capacity of 7,847 kg and flying at operational speeds around 575 kph and maximum altitudes around 18.28 km (60,000 ft), the AGS Phoenix UAV can achieve a range of some 16,113 km (8,700 NM).


The AGS programme emerged in the 1990s, aimed at providing NATO with a complete and integrated ground surveillance capability giving Alliance members unrestricted and unfiltered access to ground surveillance data in near real-time, and in an interoperable manner. Its air segment was set to comprise airborne radar sensors, and its ground segment fixed, transportable and mobile ground stations for data exploitation and dissemination, all seamlessly interconnected through high-performance data links. While a mixed fleet approach for the air segment was initially set in motion in 2004 with Airbus A321 manned aircraft and Global Hawk UAVs, both carrying versions of the TCAR radar, a NATO decision was taken to discontinue the mixed-fleet approach in 2007 due to declining European defence budgets. Instead, a simplified AGS system was agreed, with the air segment based on the off-the-shelf Northrop Grumman Global Hawk Block 40 UAV and its associated MP-RTIP sensor. In 2012, it was agreed that instead of financial input to the programme, the UK would instead make its Sentinel manned system available, and the French their then future Heron TP UAV system available to NATO’s emerging AGS capability.

That same year, a procurement contract for the AGS system was signed with prime contractor, Northrop Grumman, on behalf of the 15 NATO countries contributing to the purchase: Bulgaria, Czech Republic, Denmark, Estonia, Germany, Italy, Latvia, Lithuania, Luxembourg, Norway, Poland, Romania, Slovakia, Slovenia and the US. Northrop Grumman’s AGS industrial team includes Airbus Defence and Space, Leonardo, and Kongsberg, together with companies from all acquiring nations.

In 2015, the NATO AGS force determined the configuration of its AGS NATO RQ-4D unit in terms of staffing levels and unit structure, and that the UAVs would operate from Sigonella Air Base. In the same year, Mobile General Ground Station (MGGS) and Transportable General Ground Station (TGGS) roll-outs took place, together with the first test flight of a NATO-configured RQ-4D in the US. The first remotely-controlled test flight from Sigonella took place at the end of 2017, with temporary AGS infrastructure in place throughout the following few years, though with the construction of permanent AGS facilities scheduled to have been completed by end 2022.

The first of five permanent AGS NATO RQ-4D aircraft landed at Sigonella in November 2019; the fifth aircraft arrived one year later in November 2020, at which time formal handover of the entire AGS system to the NATO AGS Force commenced, with a first operational mission flown in November 2021. This mission saw one of the RQ-4D Phoenix aircraft take off towards the Black Sea and return 24 hours later to Sigonella proving its full operational capabilities. The challenge of this long mission focused on the airmen and soldiers operating the system, in particular their ability to hand over smoothly between shifts, including sensor operators, responsible for controlling the system’s synthetic aperture radar, who also changed over at the same time as the pilots. An initial full operational capability was achieved in February of 2022, with full and final handover completed in March.

AGS Today

Today, the NATO AGS Force at Sigonella serves as a NATO JISR deployment base and as a data exploitation and training centre. It comprises some 400 AGS personnel, though some AGS staff elements are based at Allied Command Operations in Mons, Belgium and at Allied Air Command in Ramstein. Like AWACS, AGS monitors Alliance territory, though solely to determine what is happening on the ground in relation to NATO operations.

It is an integrated system consisting of the air segment, a ground segment and a support segment. The air segment comprises the five NATO RQ-4D aircraft, which are equipped with a multi-platform radar technology insertion programme (MP-RTIP) and ground surveillance synthetic aperture radar (SAR) sensors, as well as an extensive suite of line-of-sight and beyond-line-of-sight, long-range, wideband data links.

Consisting of a number of ground stations in fixed, mobile and transportable configurations, the AGS ground segment provides high-speed data-link connectivity, data-processing, exploitation capabilities and interoperability interfaces to the system network and interfaces the AGS core system with a wide range of command, control, intelligence, surveillance and reconnaissance systems. It interconnects with multiple deployed and non-deployed operational users, and reach-back facilities away from the surveillance area.

In December 2022, sustained surge operations were conducted from Sigonella, which is now known as NATO’s Alliance Ground Surveillance Force (NAGSF), during which the multinational ISR collection force flew RQ-4Ds on four 24-hour missions on the Alliance’s eastern flank. Pilots, sensor operators, and intelligence analysts all controlled collection activities from Sigonella’s mission operation support centre.

Commander of the NAGSF Flying Squadron, USAF Lieutenant Colonel Douglas Pruitt, said the surge missions required that five different crew positions be manned continuously while the UAVs were in flight. He said that as with any operational air missions, pre-mission planning and post-mission debriefs were also required, adding, importantly, “NAGSF’s multi-national, professional aircrew are providing vital, near-real-time intelligence that is enhancing situational awareness on NATO’s eastern flank following Russia’s invasion of Ukraine.”

The NAGSF base commander at Sigonella, USAF Brigadier General Andrew Clark, said, “After declaring our initial operating capability, we increased our operational tempo faster than anticipated, with Russia’s invasion of Ukraine being the primary factor.” He added that well over 100 sorties had been flown by end 2022 and more than ‘11,000 intelligence products disseminated’. Clark said that NAGSF not only collects and distributes intelligence from its RQ-4D missions, but also – and more importantly – processes and shares so-called ‘federated intelligence products’ received from other sources, and it is this integration of these two processes that makes NAGSF a crucial specialised unit within NATO’s ISR community.

Tim Guest