Drones in energy and industry: sensitive sites, hazardous facilities and networks
Buy — €15 Contents and free extract
VAT included · secure Stripe payment · instant access to your guide after payment · terms of sale (in French)
C-DRONE GUIDE · 4 SEPTEMBER 2026
RTBA (military very-low-level network): what a professional drone operator must check before a mission
The RTBA (réseau très basse altitude, very-low-level network) is a permanent network of military restricted areas where French Air and Space Force fighter jets train to fly very low and very fast; it is only activated by segment and by time slot, published by the SIA (AZBA application and NOTAMs). On an active segment whose floor reaches the ground, no drone flies without the military authority's agreement; outside the slots, flying is possible again under the usual rules. Unlike a temporary restricted area published by NOTAM for a one-off event (see our guide to NOTAM and temporary restricted airspace), the network is permanent: a BVLOS mission, an agricultural flight or a linear-corridor inspection must check it at every preparation. Here is where to find it, how to read its activation and what it changes for a professional mission.
Published on 4 September 2026, updated on 13 October 2026 — regulations in force as of September 2026.
RTBA: a permanent military network, not a one-off restriction
The very-low-level network (RTBA) is a set of interconnected military regulated areas spread across French territory, intended for training French Air and Space Force fighter pilots to fly at very low altitude and high speed. In these corridors, aircraft can fly at heights of a few hundred feet above terrain, at speeds close to 500 knots (around 900 km/h), without the pilot being able to reliably avoid any moving obstacle encountered: that is precisely the point of the training, but it also means no separation from another aircraft, drones included, is guaranteed under these conditions.
The vertical limits of each segment are published by the aeronautical information service (SIA): on some segments the floor goes all the way down to the ground, and the whole height of the segment is then off-limits to air traffic, drones included, whenever it is active; on others the floor is set at a height (for example 800 feet), with fighter jets typically transiting around 1,000 feet (roughly 300 m). The network is shown on the 1:500,000 ICAO/VFR chart and on dedicated maps published by the SIA and the military air traffic directorate (DIRCAM). It is a structural feature of French airspace, distinct from the permanent prohibited or regulated areas around, say, nuclear power plants or certain military airfields, and also distinct from one-off restrictions published by NOTAM for a dated event.
Is the RTBA active? The AZBA application, slot table and NOTAMs
The RTBA is not permanently active: its use is organised in time slots, published for the same day and the following day on the SIA website, in the section dedicated to AZBA (low-altitude zone activity). The AZBA map shows each segment of the network, coloured by its status (active, inactive, upcoming slot), with the slot detail. Since the new version of the application put into service by the SIA (announced on 16 June 2026), the slot table for the RTBA zones opens from the button at the top right of the interface. The SIA also reminds users that the NOTAMs must be consulted to know the activation of AZBA zones; they remain available on SOFIA-briefing (sofia-briefing.aviation-civile.gouv.fr) even when the main site is under maintenance. These SIA publications are the only authoritative sources: the mere fact that a corridor appears on the ICAO chart says nothing about its status at flight time. Download them the day before if the mission site has no coverage.
The operational rule is simple to state and strict in its application: on segments where the floor reaches the ground, no take-off or transit is authorised during activation slots, except with prior agreement from the military authority managing the zone. Flying around it horizontally, or waiting out the slot, are the only options for an operator without that kind of agreement. For a mission covering a long track or crossing several segments, the check must be repeated at every stage of preparation (D-7, D-1, before take-off), exactly as for a temporary restricted area, except the information to watch is not the day's NOTAM but the AZBA schedule for the segment concerned.
Pre-flight RTBA checklist for a professional drone mission
The check comes down to five steps, repeated at each stage of preparation:
- Locate the site relative to the segments. The RTBA chart published by the SIA (alongside its 1:1,000,000 and 1:250,000 charts) and the 1:500,000 ICAO chart show the network's geography; the official France drone map (Géoportail) adds the heights allowed at the take-off point.
- Note the segment's floor and ceiling in the SIA publications (eAIP): a ground-level floor concerns every drone flight, a floor set at a height is compared with the mission's maximum height.
- Check the day's activation in the SIA's AZBA application (RTBA slot table), the day before and again just before take-off, keeping a downloaded copy if the site has no coverage.
- Cross-check with the day's NOTAMs and AIP SUPs, which cover temporary restrictions the AZBA map does not show (see our guide to NOTAM and temporary restricted airspace).
- If the segment is active: move the time slot, move the operating area out of the segment, or obtain prior agreement from the military authority managing it. In every case, keep a record of the check (screenshot, time) in the mission file.
Operator registration and mission declarations are still done on AlphaTango: the RTBA check comes on top of those steps, it does not replace them.
What this changes for a professional mission
Most open-category drone flights take place under 120 to 150 m, well below the altitudes fighter jets normally cruise at, but that is exactly the situation the RTBA creates: on ground-floor segments, a drone flight of a few dozen metres sits exactly in the volume military aircraft cross at very high speed whenever the corridor is active. The risk is not theoretical: at 900 km/h, the distance covered in one second is 250 m, leaving no margin for detection or avoidance by either aircraft. The study by Weinert, Alvarez, Owen and Zintak, published in 2022 in the Journal of Air Transportation, proposes a quantitative near-midair-collision criterion specific to small drones, precisely because the historical criteria set for manned aviation underestimate the risk posed by such asymmetric closing speeds and aircraft sizes (see the study).
Three types of professional mission are particularly affected: a BVLOS flight under the STS-01/STS-02 scenarios or an EVLOS flight on a linear corridor, which often covers several kilometres and can cross one or more network segments; an agricultural spraying or seeding mission over a large farm, flying at a height close to some segments' ground floor; and an inspection of a linear infrastructure corridor, power line, railway or pipeline, such as the one described in our guide to LiDAR vegetation clearance along high-voltage power lines, whose route can cross the network over several dozen kilometres. In all three cases, the AZBA check is an integral part of the operational safety assessment (SORA) required in the specific category, on the same footing as the analysis of overflown population or fixed obstacles.
Method and 2026 prices
For a standard mission, outside the network's segments or outside their activation slots, the AZBA check is a formality of a few minutes, folded into the usual flight preparation with no dedicated billing line. It becomes a work item in its own right as soon as a long route or a large operating area overlaps one or more segments: the route or the flight window then needs to be split according to the published slots, a postponement margin allowed for in case the schedule changes at D-1, and that analysis documented in the flight file, something the operator must be able to produce on inspection.
Ranges observed in France in 2026, excl. VAT:
| Service | Range (excl. VAT, 2026) |
| One-off AZBA check, short mission outside an active segment | included in the preparation package |
| Route analysis for a BVLOS/EVLOS mission crossing one or more RTBA segments | €200 to €500 of additional preparation |
| Re-planning an agricultural or corridor flight plan to avoid an active ground-floor segment | €150 to €400 |
| Mission postponement for an activation slot confirmed at D-1 | generally free of charge if announced more than 24 hours ahead |
The point to plan for in a brief is calendar flexibility: a BVLOS mission or an agricultural campaign planned along a route crossing the RTBA should allow for fallback windows, otherwise an activation slot announced the day before can push back a whole day's work. The regulatory information on this page reflects the rules in force in September 2026; a segment's exact activation should always be checked on the SIA's AZBA map on the day of the flight. For a BVLOS, agricultural or corridor-inspection mission, request a quote stating the route or the area covered, which allows the relevant network segments to be identified as early as the preliminary study.
Frequently asked questions
What is the RTBA?
The very-low-level network: a permanent set of interconnected military restricted areas where fighter jets train to fly very low and very fast. Each segment has a floor and a ceiling published by the SIA, and is closed to other aircraft, drones included, only during its activation slots.
How do I know whether the RTBA is active today?
By checking the AZBA map on the SIA website, which colours each segment by status and details the slots for today and tomorrow, and through the NOTAMs, which the SIA says must be consulted to know the activation of AZBA zones (also available on SOFIA-briefing). A corridor appearing on the ICAO chart says nothing about its status at flight time.
Can a drone fly in an RTBA zone?
Yes, outside the segment's activation slots. During an active slot, any flight is ruled out on segments whose floor reaches the ground, unless the military authority has agreed in advance; on a segment with a raised floor, that floor must be compared with the mission's planned maximum height.
Is the RTBA active at weekends and on public holidays?
Slots are mostly published on weekdays, but nothing allows you to assume a segment is inactive on a given day: check the AZBA map whatever the day, weekends and public holidays included.
What is the difference between the RTBA and the AZBA?
The RTBA is the network itself, i.e. the corridors and their vertical limits. The AZBA (low-altitude zone activity) is the SIA publication stating, day by day, which segments are active and when.