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Chapter 4

Airspace Control Measures

Army operations require the commander to employ a combination of positive and procedural methods of control. Common joint standing operating procedures, Army standing operating procedures, and theater specific control measures afford the necessary methods for the procedural control of airspace. The Army's airspace control methodology emphasizes the procedural control of airspace.


Methods of Airspace Control
Procedural Airspace Control Measures
      Common Joint Airspace Control
      Army Airspace Control Measures
          Standing Operating Procedures
      Air Defense Airspace Control
Fire Support Coordinating Measures
      Permissive Fire Support
          Coordinating Measures

      Restrictive Fire Support Coordinating
Deconfliction Methods
      Time Separation
      Common Reference Systems
Special Airspace Users
      Special Operations
      Unmanned Aerial Vehicle Operations
      Army Tactical Missile System


4-1. Airspace control uses positive control, procedural control, or a combination of both. Positive control is conducted by elements designated by the airspace control authority (ACA). It relies on positive identification, tracking, and direction of aircraft in the airspace control area. It uses electronic means such as radar; sensors; identification, friend or foe (IFF) systems; selective identification feature capabilities; digital data links; voice; and other identification methods. Procedural control is used when positive control is not possible and relies on a combination of mutually agreed and promulgated orders and procedures. These may include comprehensive air defense (AD) identification procedures, rules of engagement, aircraft identification maneuvers, fire support coordinating measures (FSCMs), and airspace control measures (ACMs). Service, joint, and multinational capabilities and requirements determine which methods or elements of each that the airspace control plans and systems use.


4-2. As discussed in Chapter 1, the joint force commander (JFC) designates an ACA to develop, coordinate, and publish airspace control procedures for operating the airspace control system in the joint operations area. He establishes an airspace control plan, which includes procedural ACMs—such as, restricted operations areas (ROAs), high-density airspace control zones (HIDACZs), and minimum-risk routes (MRRs)—defensive ACMs, and FSCMs. The airspace control plan provides specific planning guidance and procedures to support various operation plans of a joint or multinational force. The airspace control order implements the airspace control plan and provides the details of the approved requests for ACMs.

4-3. Airspace control measures are rules, mechanisms, and directions governed by joint doctrine and defined in the airspace control plan. These measures control how to use airspace of specified dimensions. Airspace elements establish ACMs to accomplish one or more functions:

  • Establish reserved airspace for specific airspace users.

  • Restrict the actions of some airspace users.

  • Create airspace in which units can use weapons with minimal risk of fratricide.

  • Control actions of specific airspace users.

  • Require airspace users to accomplish specific actions.


Common Joint ACMs

  • Coordinating Altitude
  • Low-Level Transit Route
  • Minimum-Risk Route
  • Restricted Operations Area
  • Special-Use Airspace
  • High-Density Airspace Control Zone
  • Standard Use Army Aviation Flight Routes

4-4. The joint commands agreed on several ACMs used by Army airspace command and control (A2C2) elements. JP 3-52 provides additional information on each listed airspace control measure as well as information on other ACMs used by A2C2 elements.

Coordinating Altitude

4-5. Coordinating altitude is a procedural airspace control method used to separate fixed- and rotary-wing aircraft. This method determines an altitude below which fixed-wing aircraft will normally not fly and above which rotary-wing aircraft normally will not fly. The coordinating altitude is normally specified in the airspace control order and may include a buffer zone for small altitude deviations (JP 3-52). Figure 4-1 illustrates this method. The coordinating altitude can vary from theater to theater and even within a theater. It does not prohibit using fixed- or rotary-wing aircraft in airspace above or below the coordinating altitude; however, aircraft that need to cross the coordinating altitude should coordinate with the appropriate controlling agency before they penetrate it. When aircraft pass into the airspace above or below a coordinating altitude, control3/4 either positive or procedural3/4 always reverts to the controlling authority for that airspace. Coordinating altitudes do not apply to air defense artillery (ADA) or field artillery fires.

Figure 4-1. Coordinating Altitude

Figure 4-1. Coordinating Altitude

Low-Level Transit Route

4-6. A low-level transit route (LLTR) is a temporary corridor established in the forward area to minimize risk to friendly aircraft from friendly AD or surface forces (JP 3-52). These routes are used only within NATO. The ACA specifies how many LLTRs to establish to accommodate air operations. Division and corps commanders nominate LLTR ground traces. The A2C2 element plans the actual LLTRs with Air Force coordination and assistance. A well-planned LLTR accommodates transiting aircraft by being oriented on terrain features that allow easy visual navigation. Aircraft should also avoid critical areas and assets defended by ADA and areas of anticipated intense combat operations, such as the objective of the decisive operation. Additionally, airspace elements establish the corridor to avoid3/4

  • Field artillery positions.

  • Targets planned for engagement with ground-based systems.

  • Landing zones, pickup zones, forward arming and refueling points, landing sites, and airfields.

  • Known enemy ADA locations.

  • Other planned or active special-use airspace (for example, ROAs, HIDACZs, or special corridors).

Minimum-Risk Route

4-7. A minimum-risk route is a temporary corridor of defined dimensions recommended for use by high-speed, fixed-wing aircraft that presents the minimum known hazards to low-flying aircraft transiting the combat zone (JP 3-52). See Figure 4-2 for a graphic illustration. The dimensions of a MRR vary; the route may change frequently and may extend below the coordinating altitude. MRRs are established considering the threat, friendly operations, terrain, known restrictions, and fire support locations. Ground commanders nominate MRRs through the A2C2 system to the ACA. Friendly fixed-wing aircraft on cross-forward line of own troops missions primarily use these routes.

Figure 4-2. Minimum-Risk Route

Figure 4-2. Minimum-Risk Route

Restricted Operations Area

Figure 4-3. Restricted Operations Area

Figure 4-3. Restricted Operations Area

4-8. As seen in Figure 4-3, a restricted operations area is that airspace of defined dimensions created in response to specific operational situations or requirements within which the operation of one or more airspace users is restricted. It is also known as a restricted operations zone (ROZ) (JP 3-52). The ROA or ROZ significantly helps to deconflict surface attacks, prevent duplicated effort, and prevent fratricide by closely restricting airspace access over a designated surface area.

4-9. Maneuver commanders request ROAs or ROZs; the ACA approves them. Commanders use ROAs or ROZs to support many types of operations. Some typical uses are to restrict air operations over Army Tactical Missile System (ATACMS) launch and target areas as well as unmanned aerial vehicle (UAV) launch and recovery areas.

Special-Use Airspace

4-10. Special-use airspace is an area of airspace reserved for a specific purpose and is established by the ACA. It may also designate airspace in which no flight activity is authorized. Special-use airspace typically applies to base defense zones, combat air patrol (CAP) and orbit areas. See JP 3-52 for more details. Location, orientation, altitude, and time define CAP and orbit areas. They allow the joint force air component commander (JFACC) and other component commanders to pre-position air assets for surveillance, reconnaissance, air defense, battle management, and anticipated air strikes.

High-Density Airspace Control Zone

Figure 4-4. High-Density Airspace Control Zone

Figure 4-4. High-Density Airspace
Control Zone

4-11. A high-density airspace control zone is an area in which there is a concentrated employment of numerous and varied weapons or airspace users (JP 3-52). This zone restricts airspace use because of the large volume and density of fires supporting ground operations within the described geographical area. See Figure 4-4. A HIDACZ has defined dimensions, which usually coincide with geographical features or navigational aids. A ground commander requests a HIDACZ and the ACA approves it.

4-12. By establishing a HIDACZ, the ground commander forces other airspace users either to operate elsewhere or under the conditions and restrictions that he has established. The A2C2 element of the requesting headquarters for a HIDACZ must be prepared to provide the following guidance and directions for all airspace users:

  • Low-level transit routes and minimum-risk routes into and out of the HIDACZ.

  • Fire support coordination.

  • Air traffic advisory.

  • ADA weapons control status coordination.

  • Enemy unit locations.

  • Procedures for expeditious movement of aircraft into and out of the HIDACZ.

Standard Use Army Aircraft Flight Routes

4-13. Ground commanders establish standard use Army aircraft flight routes (SAAFRs) below the coordinating altitude to provide safe routes for aviation assets performing combat support and combat service support missions. Figure 4-5 shows a SAAFR. These routes do not need ACA approval if they remain below the coordinating altitude. If a coordinating altitude has not been established, then the requesting ground commander must get approval from the ACA. The A2C2 element must report SAAFRs to the ACA, and SAAFRs must appear on all A2C2 overlays. The A2C2 element at each echelon must develop the SAAFR structure in each respective area of operation.

Figure 4-5. Standard Use Army Aircraft Flight Routes

Figure 4-5. Standard Use Army Aircraft Flight Routes


Standing Operating Procedures

  • Air Corridor
  • Axis of Advance
  • Air Control Point
  • Battle Position
  • Engagement Area
  • Communications Checkpoint
  • Attack by Fire Position
  • Observation Post

4-14. The Army, in addition to the common joint ACMs, has developed standardized control measures. These measures assign responsibility; ensure conformity with the tactical plan; describe and illustrate the concept of operations; maintain separation of forces; concentrate effort; coordinate fires with maneuver; and assist in the command and control of forces. When Army forces incorporate airspace control measures with these standard control measures, they can graphically depict the integration, coordination, regulation, and identification of Army airspace users in a given area of operation. These measures are air corridor, axis of advance, air control point, battle position, engagement area, communications checkpoint, attack by fire position, and observation post.

Air Corridor

4-15. An air corridor is a restricted air route of travel specified for use by friendly aircraft and established for the purpose of preventing friendly aircraft from being firing on by friendly forces (JP 3-52). See Figure 4-6. Air corridors are used to route combat aviation elements between such areas as forward arming and refueling points, holding areas, and battle positions. These corridors also deconflict artillery firing positions with aviation traffic, including UAVs. Altitudes of an air corridor do not exceed the coordinating altitude. If a coordinating altitude has been established, the ground force commander implements an air corridor. If a coordinating altitude has not been established, the ACA, at the request of the ground commander, establishes an air corridor.

Axis of Advance

Figure 4-6.  Air Corridor and Axis of Advance

Figure 4-6. Air Corridor and Axis of Advance

4-16. An axis of advance is a general route of advance, assigned for the purposes of control, which extends toward the enemy. The axis of advance symbol graphically portrays a commander's intention, such as avoiding built-up areas or known enemy air defense sites. When used for attack aviation operations, it provides the general direction of movement and may be subdivided into routes. See FM 3-90.

Air Control Point

4-17. An air control point is an easily identifiable point on the terrain or an electronic navigational aid used to provide necessary control during air movement. Air control points are generally designated at each point where the flight route or air corridor makes a definite change in any direction and at any other point deemed necessary for timing or control of the operation. It is used to develop the routes for SAAFRs, LLTRs, and MRRs. Preplanned air control points facilitate the rapid restructuring of routes.

Battle Position

4-18. A battle position is a designated area in which attack helicopters can maneuver and fire into a designated engagement area or can engage targets of opportunity. Elements assigned a battle position will locate within the general area (as outlined by the battle position) and may move within the outline of the battle position. See FM 3-90.

Engagement Area

4-19. An engagement area lies along an enemy avenue of approach where the commander intends to contain and destroy an enemy force with massed fires of all available weapons. When multiple airspace users operate simultaneously, A2C2 elements will provide detailed planning and coordination to deconflict the airspace. See FM 3-90.

Communications Checkpoint

4-20. The communications checkpoint is a type of air control point. It requires serial leaders to report to either the aviation mission commander or to the terminal control facility.

Attack by Fire Position

4-21. An attack by fire position designates the general position from which a unit conducts the tactical task of attack by fire. The purpose of these positions is to increase the supported force's freedom of maneuver; it does not indicate a specific site. See FM 3-90.

Observation Post

4-22. An observation post is a position from which soldiers make observations or direct and adjust fires. This post possesses appropriate communications. It may be airborne. See FM 3-90.


ACMs for Air Defense

  • Base Defense Zone
  • Weapon Engagement Zone
  • Weapons Free Zone
  • Air Defense Identification Zone

4-23. Airspace control and air defense operations are linked inextricably in enemy engagement operations. Because of this link, airspace control measures used for air defense must be part of the A2C2 plan. The A2C2 elements must plan and coordinate, in detail, these control measures. The ACMs may be requested by the A2C2 elements and submitted to the area air defense commander (AADC) for approval and inclusion on the airspace control order (ACO). Some common procedural ACMs used in air defense operations are listed. FM 3-52.1 and JP 3-52 provide additional information.

Base Defense Zone

4-24. A base defense zone is an air defense zone established around an air base and limited to the engagement envelope of short-range air defense weapon systems defending that base (JP 3-52). Base defense zones as shown in Figure 4-7 have specific established entry, exit, and IFF procedures. The base defense zone may be thought of as a specific type of ROA or special-use airspace.

Figure 4-7. Base Defense Zone

Figure 4-7. Base Defense Zone

Weapon Engagement Zone

4-25. Weapon engagement zones (WEZs) are airspace of defined dimensions within which the responsibility for engagement of air threats normally rests with a particular weapon system (JP 3-52). Examples of weapon engagement zones include the high-altitude missile engagement zone, low-altitude missile engagement zone, fighter engagement zone, joint engagement zone, and short-range air defense engagement zone. The area defined by the WEZ depends on specific weapon system capabilities.

Weapons Free Zone

4-26. The weapons free zone is an air defense zone established for the protection of key assets or facilities, other than air bases, where weapon systems may be fired at any target not positively recognized as friendly (JP 3-52). See Figure 4-8. It is used for high-value asset defense and in areas with limited command and control authority. The AADC declares the zone weapons free and the ACA approves the requested zone.

Figure 4-8.  Weapons Free Zone

Figure 4-8. Weapons Free Zone

Air Defense Identification Zone

4-27. An air defense identification zone (ADIZ) is airspace of defined dimensions within which the ready identification, location, and control of airborne vehicles are required (JP 3-52). The ADIZ is associated with nations or areas of operations and is normally the transition between procedural and positive control areas. This zone is used for sovereign national boundaries or, in the case of military operations, for identification into the rear areas. ADIZs are theater specific and established by the AADC.



  • Permissive FSCMs
    • Free-Fire Area
    • Coordinated Fire Line
    • Fire Support Coordination Line
  • Restrictive FSCMs
    • Airspace Coordination Area
    • Restricted Fire Line
    • No-Fire Area
    • Restricted Fire Area

4-28. Fire support coordinating measures are important elements in any A2C2 plan. Integrating the FSCMs and ACMs can be extremely difficult. The measures are not complementary and may cause conflicts between airspace users and fire delivery systems. All indirect fires pose a potential hazard to other friendly airspace users. The highest probability of conflict occurs at relatively low altitudes in the immediate vicinity of the firing unit and target location. Commanders incorporate FSCMs to facilitate rapidly engaging targets while simultaneously providing safeguards for friendly forces. Fire support coordination associated with A2C2 occurs at all levels, from the fire support officer at the maneuver battalion command post to the fire support elements at each higher echelon. The G3/S3 ensures integration of the fire support mission through A2C2. A2C2 elements must work with fire support elements and tactical air control parties to ensure that appropriate FSCMs and ACMs are planned, requested, and approved to support the ground commander's scheme of maneuver. Properly planned and coordinated FSCMs and ACMs do not restrict the ground commander's ability to effectively employ fires in support of maneuver. FSCMs are divided into permissive and restrictive measures. See JP 3-09 and FM 3-09 for discussions on FSCMs.


Free-Fire Area

4-29. A free-fire area (FFA) is a specific designated area into which any weapons system may fire without additional coordination with the establishing headquarters (JP 3-09). Only the commander with jurisdiction over the area—usually a division or higher commander—may establish a FFA. The FFA should be located on identifiable terrain; however, grid coordinates may designate it.

Coordinated Fire Line

4-30. The coordinated fire line (CFL) is a line beyond which conventional—direct and indirect—surface fire support means may fire at any time in the boundaries of the establishing headquarters without additional coordination. Its purpose is to expedite the surface-to-surface attack of targets beyond the CFL without coordination with the ground commander in whose area of operation the targets are located. A brigade or division commander usually establishes the CFL.

Fire Support Coordination Line

4-31. The fire support coordination line (FSCL) facilitates the expeditious attack of targets of opportunity beyond the coordinating measure. It does not divide an area of operations (AO). It applies to all fires of all weapon systems using any munitions against surface targets. The appropriate land commanders—in consultation with superior, subordinate, supporting, and affected commanders—establish and adjust the FSCL in their boundaries. Changing the FSCL requires notifying all the affected forces in the AO and must allow sufficient time for these forces to incorporate the change. FM 3-09 discusses fire support coordination lines.


Airspace Coordination Area

4-32. The airspace coordination area is a three-dimensional block of airspace in a target area, established by the appropriate ground commander, in which friendly aircraft are reasonably safe from friendly surface fires. The airspace coordination area may be formal or informal (JP 1-02). This area facilitates the simultaneous attack of a target or target near each other by multiple assets, usually air and surface-to-surface fires. The Army defines an airspace coordination area as a block or corridor of airspace in which friendly aircraft are reasonably safe from friendly surface fires. The airspace coordination area may be formal or informal.

4-33. Formal Airspace Coordination Area. Formal airspace coordination areas require detailed planning. The vertical and lateral limits of such areas allow freedom of action for air and surface fire support against the greatest number of targets. The airspace control authority establishes formal airspace coordination areas at the request of the appropriate ground commander (normally brigade and higher level). Information defining a formal airspace coordination area includes minimum and maximum altitudes, a baseline designated by grid coordinates at each end, the width (on either side of the baseline), and the effective times. See Figure 4-9.

Figure 4-9. Formal Airspace Coordination Area

Figure 4-9. Formal Airspace Coordination Area

4-34. Informal Airspace Coordination Area. At the request of subordinate A2C2 elements, the ground commander can ask the ACA to establish informal airspace coordination areas. An informal airspace coordination area can be established at battalion task force level or higher. Aircraft and surface fires may be separated by time or distance (laterally, by altitude, or by a combination of lateral or altitude). Distance separation requires less-detailed coordination between aircraft and firing units, but it can be the most restrictive for aircraft routing. Fire support personnel should select the separation technique that requires the least coordination without adversely affecting the aircrew's ability to safely complete the mission.

Restrictive Fire Line

4-35. A restrictive fire line (RFL) is a line established between converging friendly surface forces that prohibits fires or their effects from crossing that line. The purpose of the RFL is to prevent fratricide and duplication of attacks by converging friendly forces. The commander common to both friendly forces establishes the RFL (JP 3-09).

No-Fire Area

4-36. A no-fire area (NFA) is a land area designated by the appropriate commander in which fires or their effects are prohibited. There are two exceptions. The first exception is when the establishing headquarters approves fires in the NFA on a mission-by-mission basis. The second is when an enemy force within the NFA engages a friendly force, the commander may engage the enemy to defend his force. It is established on identifiable terrain (if possible), by grid coordinates, or by a radius from a center point (FM 3-09).

Restrictive Fire Area

4-37. A restrictive fire area (RFA) is an area in which specific restrictions are imposed and into which fires that exceed those restrictions will not be delivered without coordination with the establishing headquarters. A maneuver battalion or higher commander normally establishes RFAs. The RFA is established on identifiable terrain, by grid, or by a radius from a center point.


4-38. Despite detailed planning and coordination, airspace conflicts will arise. All echelons of A2C2 elements must be prepared to deconflict airspace, facilitate using weapons platforms, and prevent fratricide. All A2C2 plans should include some deconfliction methods. Two examples of deconfliction methodologies are time separation and common reference system.


4-39. Time separation requires detailed coordination. It may be required when aircraft, manned and unmanned, must fly near indirect-fire trajectories or ordnance effects. This procedure requires extensive coordination between the fire support coordinator and the A2C2 element. The timing of surface fires must be coordinated with aircraft routing. This ensures that even though aircraft and surface fires may occupy the same space, they do not do so at the same time. All timing for surface fires is based on the specific aircraft event time—time on target and time to target. Time separation works appropriately when aircrews and firing units engage the same or nearby targets.


4-40. Common reference systems provide a universal perspective with which to define specific areas of the battlespace, enabling commanders to efficiently coordinate, deconflict, and synchronize surface attacks. These systems result in rapid, deconflicted surface attacks; enhanced probability of mission success; and reduced potential for duplicated effort and fratricide. They also allow for rapidly coordinating joint engagement and employing combined arms. Such systems are flexible enough to use for other purposes, such as labeling search and surveillance areas, identifying restricted zones, and designating high-threat areas—such as enemy surface-to-air missile battery locations. These systems primarily provide the force with a common frame of reference. One such system is the Bullseye Reference System found in FM 3-52.1. JP 3-60 discusses the details of common reference systems.



4-41. Special operations present a distinct challenge for Army airspace command and control. A2C2 elements must coordinate and deconflict special operations with conventional operations (to the battalion level) primarily via liaison with established conventional command and control agencies. The special operations liaison element (SOLE) coordinates and synchronizes special operations forces (SOF) air and surface operations with joint air operations for the joint force special operations component commander.

4-42. Restrictive fire areas, no-fire areas, or possibly ROAs can protect most areas of special operations. The A2C2 element coordinates these areas with the SOLE, special operations coordination element (SOCOORD), and special operations command and control element (SOCCE), which know the locations and activities of SOF in and outside of the area of responsibility.

4-43. Clandestine special operations, which do not permit published control measures, require direct coordination and deconfliction by the SOLE, SOCOORD, or SOCCE. Should proposed conventional operations put special operations at risk (by the ATACMS or deep attack by Army aviation or UAV operations), then the SOLE, SOCOORD, or SOCCE must deconflict or recommend disapproval because of the potential for fratricide or compromise.


4-44. UAVs provide a significant challenge due to their small size, agility, and increasing density as well as their limited ability to detect, see, and avoid other aircraft. UAVs pose an operational hazard to manned aircraft operating nearby. UAV flights, like manned aircraft flights, must be coordinated to ensure deconfliction with other airspace users. UAV missions should be coordinated with the ACA, AADC, and the JFACC to safely separate UAVs from manned aircraft and to prevent engagement by friendly air defense systems.

4-45. The ACA may establish specific UAV flight routes and altitudes and publish them in the airspace control plan. The established principles of airspace management used in manned flight operations normally apply to UAV operations but may be waived by the JFC. UAV missions may be both preplanned and immediate in nature. Preplanned UAV flights should be included in the air tasking order, special instructions, or ACO. Immediate UAV missions will be coordinated with the appropriate airspace control agencies to safely separate UAVs from manned aircraft and to prevent inadvertent engagement by friendly air defense elements. Specific tactics, techniques, and procedures (TTP) for using UAV are in JP 3-55.1 and FM 3-52.1.


4-46. Corps or echelon above elements usually plan or request ATACMS operations. The key elements involved in ATACMS deconfliction are the corps fire support element, corps A2C2 element, battlefield coordination detachment, air support operations center, and the joint air operations center. ATACMS missions may be preplanned or immediate. TTP for the airspace deconfliction of the ATACMS missions may be found in FM 3-52.1.

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