Coordination

General

The Role of Coordination

Coordination helps controllers stay aware of aircraft that are about to enter their jurisdiction and ensure they will operate in a predictable manner, which allows for easier planning of sequencing and separation. Controllers must engage in constant communication to resolve potential conflicts, hand off aircraft, and maintain the integrity of established traffic flows. In high-density airspace with multiple sectors, controllers must often rely on coordination with adjacent units to address traffic complexities that cannot be resolved within a single sector.

When receiving a coordination call, respond by stating your position. If you are busy, ask the other controller to standby. If the delay will be significant, inform them that you will call back. Each instruction, clearance, or change must be verbalized once by each controller to confirm understanding. If multiple changes are discussed and not yet verbalized by both parties, a readback is required.

Standardised operating procedures and letters of agreement (LoA) define many of these handover conditions, detailing the required flight levels, routing, and speed constraints for transferring aircraft. However, real-time adjustments are often necessary due to weather changes, unexpected congestion, or airspace limitations. Effective coordination ensures that all necessary deviations are communicated and agreed upon between controllers.

Principle of Receiving Unit Control

A core concept in air traffic management is that "the receiving unit sets the entry conditions." This means the sector accepting an aircraft determines the required altitude, speed, and routing.

For instance, if Sector 1 hands off to Sector 2, and Sector 2 mandates aircraft to enter at FL290, speed 280 knots, and a direct route to a designated waypoint, then Sector X is responsible for ensuring compliance before the transfer. While adjustments and negotiations are always possible, this principle ensures clarity and consistency in traffic handling.

Point-to-Point Coordination

Coordination must follow a point-to-point structure, meaning you can only coordinate with the sector the aircraft is arriving from or going to—no skipping sectors.

Example:
If an ACC controller needs to pass an amended route to an aircraft on the ground, they cannot coordinate directly with GND or TWR if the aircraft is currently under APP’s control. Instead, ACC must coordinate with APP, and it is then APP’s responsibility to pass the coordination down the line as needed.

Best Practices for Effective Coordination

All coordination must be clear and unambiguous. Not all controllers will strictly follow phraseology rules, so when using plain language, ensure both parties fully understand the message.

To ensure smooth coordination, controllers should:

Early notification and strategic communication facilitate a smoother workflow and prevent operational disruptions.

Key Considerations

TWR/GND

Effective coordination between ATC units is essential for safe and efficient air traffic management. While many procedures are defined in SOPs, some situations require direct controller-to-controller coordination to handle non-standard operations effectively.

Coordination Between TWR) and APP

Tower and Approach controllers must coordinate in various scenarios, including:

Coordination Between Tower (TWR) and Ground (GND)

Efficient communication between TWR and GND is necessary in situations such as:

Coordination Guidelines

Unlike some Approach and Center coordination, Tower and Ground coordination does not follow strict phraseology. Instead, controllers should use clear and concise plain language to keep communication brief and efficient—especially when the receiving controller is busy with pilot interactions.

Example Coordination Exchanges

Tower and Approach Coordination

TWR → APP:

"Approach, Tower."

APP → TWR:

"Go ahead."

TWR → APP:

"TUN988 cannot fly SIDs and needs direct MEDIL. What vectored departure should I issue?"

APP → TWR:

"Climb runway track to 4000 feet, expect radar vectors."

TWR → APP:

"Copied."

Tower and Ground Coordination

TWR → GND:

"Ground, Tower."

GND → TWR:

"Go ahead."

TWR → GND:

"KMR112 mis-taxied, now coming via J5 instead of J2."

GND → TWR:

"Roger."

Class D Airspace Coordination

ACC/APP → Class D Tower (Heads-Up Coordination)

For arrivals or overflights, coordination should be completed at least 5 minutes before the boundary.

Format for Verbal Coordination

"Via (Route/Procedure), (Callsign), (Level - if different from standard), (Runway - if not duty runway)"

Class D Tower → Enroute/Approach (Next Call Coordination)

For all CTA/TMA departures, the next call must be made within 2 minutes of takeoff.

Radar Tower Coordination

Radar Tower → Approach (APP) Coordination

Timing Requirement
Phraseology Example: Cancelling Auto Release

APP → TWR:

"Cancel Auto Release."

TWR → APP:

"Cancel Auto Release, MAC477T released."

APP → TWR:

"MAC477T."

Approach (APP) → Radar Tower Coordination

Auto Release Suspension

If Auto Release must be cancelled due to weather, overflying aircraft, or runway configuration changes, APP must notify the ADC controller.

APP/ACC

Upstream and Downstream Sectors

Example
If an aircraft transitions through Sector A → B → C:

Coordination Point (COP)

A Coordination Point (COP) is a designated waypoint near a sector boundary where aircraft are handed off between controllers.

Common COP types:

Controllers should use well-known waypoints, VORs, or major aerodromes when coordinating handoffs. In VATSIM, specifying the exact location of an aircraft is useful since pre-planned coordination is less structured than in real-world operations.

Transfer of Control

The transfer of control occurs when responsibility for issuing flight instructions (altitude, heading, speed) moves from one controller to another.

Unless otherwise specified in a Letter of Agreement (LoA) or verbal coordination, control is transferred when the aircraft enters the new sector and has reached half of the required minimum separation distance from the boundary.

Example

This ensures that both sectors maintain full separation without additional coordination.

Silent Transfer of Control

In some cases, an LoA allows for silent transfer of control, meaning an aircraft can be handed off without requiring additional verbal coordination.

This applies when:

Certain routes, levels, and airspace have predefined silent coordination agreements, eliminating the need for verbal coordination. However, restrictions may still apply, preventing changes close to sector boundaries.

Handoffs

A handoff occurs when control of an aircraft is transferred between controllers.

Once a receiving controller accepts a handoff, they can:

Handoff Restrictions

Full Control After Handoff

Transfer of Communication

A transfer of communication happens when an aircraft is instructed to switch to a new ATC frequency.

For example, a controller may hand off communication early while still retaining control of the aircraft for sequencing or separation purposes.

Controller Initials in Coordination

In real-world ATC, controllers are identified by unique initials (formed from their first and last names).

During verbal coordination, initials are exchanged as a confirmation that both controllers agree on the handover.

Approval Request

When a controller needs approval from another sector for a specific action, an Approval Request is used.

This is common for:

  1. Direct Routing Requests
  2. Climbing or Descending Across a Sector Boundary
  3. Deviations from Agreed Flight Levels

Each type of request follows a standard format to ensure clarity and efficiency in coordination.

Direct Routing Request (Downstream Coordination)

Granting a direct-to waypoint clearance can improve efficiency, accommodate pilot requests, or resolve conflicts. Within a controller's own sector, this can be done without coordination. However, if the waypoint is in an adjacent sector, approval from the downstream controller is required.

This request can be made using Euroscope coordination functions or verbally.

Format for Verbal Coordination

APPROVAL REQUEST <COP/position> <call sign>
DCT <waypoint>

Procedure
  1. Contact the receiving sector and wait for their "Go ahead" response.
  2. This allows the receiving controller to check the aircraft’s position and potential conflicts.
  3. Once permission is granted, the request is either approved or denied.

Climbing/Descending at Sector Boundaries

By default, aircraft should be level when crossing a sector boundary unless an LoA (Letter of Agreement) states otherwise.

Format for Verbal Coordination

APPROVAL REQUEST <COP/position> <call sign>
CLIMBING <level> / DESCENDING <level>

Deviation from Agreed Flight Level

If an aircraft must cross a sector boundary at a different level than agreed in the LoA, coordination is required. This can be done using:

Clearing Through a Third-Party Sector

If an aircraft requires clearance through a sector that is not normally involved, additional coordination is needed.

Format for Verbal Coordination

APPROVAL REQUEST FOR AIRSPACE CROSSING <call sign> <position>
CLIMB UP TO FLxxx (routing) / DESCEND DOWN TO FLxxx (routing)

This is often mistaken for a release, but it is strictly an approval request. Releases are discussed in a separate section.

If the previously uninvolved sector assumes full control of the aircraft or takes over from the originally planned downstream sector, an additional request format is used:

APPROVAL REQUEST FOR ADDITIONAL TRAFFIC AIRBORNE MARRAKECH <call sign>
DCT SLK FL300

This shifts the responsibility of further downstream coordination to the accepting sector.

Boundary Coordination

Boundary coordination is required when an aircraft is expected to deviate within half of the required separation for another sector’s airspace.

This applies if an aircraft is within:

Boundary coordination informs the adjacent sector about the aircraft and allows them to impose restrictions if necessary.

Format for Verbal Coordination

For Ident, (Position), (Callsign), (Details as required)

(Callsign), (Restriction)

Example Phraseology

SOU → NOR: "For Ident, overhead SAK, RAM12, do you have any restrictions on descent?"
NOR → SOU: "RAM12, No restrictions on descent."

If the boundary sector has no restrictions, they may omit the restriction and simply read back the callsign. This confirms that no vertical or lateral restrictions apply.

Example Phraseology with Omission

WES → EAS: "For Ident, west of RAVMA, AB123"
EAS → WES: "AB123"

Spacing Below Standard Separation

Silent transfers of control typically requires 10 NM separation at the same speed. The following rules apply when transferring aircraft at the same flight level:

Condition Required Separation
Leading aircraft is at the same speed or faster 10 NM
Trailing aircraft is up to 20 knots / M0.05 faster 20 NM
Trailing aircraft is up to 40 knots / M0.10 faster 30 NM
Example Scenario

Two aircraft are transferred with 15 NM separation, but the trailing aircraft is 30 knots faster.

Format for Coordination

APPROVAL REQUEST <COP/position> <call sign>
<distance> <speed difference>

Release Coordination

A release allows the receiving sector to issue instructions before an aircraft crosses the sector boundary and control is officially transferred.

Types of Releases
Type of Release Purpose
Turn Release Allows a turn up to 45 degrees left or right before control transfer.
Climb Release Allows the receiving sector to issue a climb before control transfer.
Descent Release Allows the receiving sector to issue a descent before control transfer.
Full Release Grants full control (turns, climbs, and descents) before transfer.

Requesting a Release

A release can be sent with the handoff via Euroscope (TopSky plug-in), but if this is not done, the receiving sector must request the release verbally.

Format for Verbal Request

REQUEST RELEASE <callsign>

Example Phraseology

NOR → SOU:

"REQUEST RELEASE (FOR (RIGHT/LEFT) TURNS / FOR CLIMB / FOR DESCENT) RAM123"

SOU → NOR:

"RAM123 RELEASED (FOR (RIGHT/LEFT) TURNS / FOR CLIMB / FOR DESCENT) <initials>"

NOR → SOU:

"<initials>"

A Coordination Point (COP) is not required in this communication.

Release Subject to Discretion (SYD)

A Release Subject Your Discretion (SYD) is used when the releasing sector has other aircraft that may impact the release.

Example of SYD Release

NOR → SOU:

"REQUEST RELEASE RAM123"

SOU → NOR:

"RAM123 RELEASED SYD RYR123 overhead FOBAC on R722, FL290 <initials>"

NOR → SOU:

"<initials>"

Explanation

The key to SYD releases is ensuring both controllers clearly understand who is responsible for separation.

Heads-Up Coordination

Heads-up coordination is used to notify the next sector about an incoming aircraft.

Format for Verbal Coordination

(Position), (Callsign)

(Callsign), (Level)

Example Phraseology

NOR → SOU:

"Via SLK, RAM1234"

SOU → NOR:

"RAM1234, F350"

If the assigned level at transfer of jurisdiction is different from the current CFL, the controlling sector must specify:

"Will be assigned (level)."

If the receiving sector needs a different level, they will respond with the amendment.

Example Phraseology with Level Change

NOR → SOU:

"Via SLK, RAM1234"

SOU → NOR:

"RAM1234, F300 due traffic"

NOR → SOU:

"F300, RAM1234"

Once coordination is completed, the aircraft’s level and route are locked in.
Any further changes must be re-coordinated.

Best Practice

Reference Calls

When an action does not fit an Approval Request or Release, a Reference Call is used.

Primary Use Case
Example Reference Call

SOU → NOR:

"REFERENCE SLK RAM123"
"REFERENCE 20 MILES WEST OF SLK RAM123"

NOR → SOU:

"Go ahead"

SOU → NOR:

"REQUEST HIM DIRECT MABAP"
"REQUEST HIM DCT MAK, DESCENDING FL90"
"REQUEST HIM AT FL200"
"REQUEST HIM AT SPEED 250 KNOTS"

NOR → SOU:

"CONSIDER <initials>"
"WILCO <initials>"
"UNABLE <initials>"

SOU → NOR:

"<initials>"

Reference Call Responses

Using Reference Calls for Requests

A Reference Call can also be used instead of an Approval Request for open-ended coordination.

Format for Verbal Coordination

REFERENCE <COP/position> <callsign>
REQUEST HIGHER/LOWER LEVEL

Common Uses

If an aircraft has not yet completed a crossing, a Reference Call allows controllers to coordinate a higher/lower level for smoother sequencing.

Departure Release Requirements

At certain airports, a Departure Release must be obtained from the radar sector before each IFR departure.

Departure Release Coordination

If a release is required, coordination follows this structure:

Format for Verbal Coordination

TWR → Radar (APP/ACC):

"REQUEST RELEASE RAM123"

Radar (APP/ACC) → TWR:

"RAM123 RELEASED <initials>"
"RAM123 RELEASED AFTER LANDING RYR123 <initials>"
"RAM123 RELEASED, CLEARANCE EXPIRES AT 1530 <initials>"
"RAM123 RELEASED AT 1520 <initials>"
"UNABLE, CALL YOU BACK <initials>"

TWR → Radar (APP/ACC):

"<initials>"

If a release is denied, the radar controller will call back when the departure is approved.

Next Coordination

Departure release coordination is conducted between TWR and APP/ACC controllers to determine the next aircraft to depart.

Format for Verbal Coordination

TWR → APP:

"Next, (Callsign), (Runway)"

APP → TWR:

"(Callsign), (Runway), (Lateral and/or Vertical Instructions)"

Departure Instructions

Instruction Meaning
Left/Right Turn Make a visual left/right turn to establish on the planned outbound track.
Left 180 At the SID turn height (or safe altitude for visual departures), fly heading 180.
Left 180 Visual Same as above, but the pilot must maintain visual separation from terrain.
Extended Runway Centerline Track the extended runway centerline (accounting for drift).

Note: "Unrestricted" is not a readback item.

Example Phraseology

Visual Departure Example (LAM departing from GMAD)

TWR → APP:

"Next, LAM, runway 27"

APP → TWR:

"LAM, runway 27, left turn, unrestricted"

TWR → APP:

"Left turn, LAM"

Procedural SID Example (EZY342 from GMAD, Auto Release cancelled)

TWR → APP:

"Next, EZY342, runway 27"

APP → TWR:

"EZY342, unrestricted"

Airways Clearance Coordination

At some aerodromes, TWR must coordinate with APP/ACC before issuing an airways clearance for certain aircraft.

Format for Verbal Coordination

TWR → ACC:

"(Callsign) requests clearance to (Destination), (Any Other Relevant Details)"

ACC→ TWR:

"(Callsign), clearance approved"

Example Phraseology

TWR → ACC:

"AB213 requests clearance to Fez"

ACC → TWR:

"AB213, clearance approved"

If a level change or route adjustment is required, APP/ACC will provide the update during the exchange.

Important Considerations
Types of Departure Clearance Responses
Response Type Meaning
Approved Without Restriction Immediate clearance is granted.
Approved With Restriction Clearance is conditional (e.g., after an arrival lands or before a set time).
Denied The departure is not possible at the moment; APP/ACC will call back when clearance is available.

Clear understanding of these responses ensures smooth coordination and efficient traffic flow.

Estimate Coordination (Not Relevant for VATSIM)

In real-world ATC, an Estimate Call is used to exchange an aircraft’s:

Most estimates are automatically exchanged through flight data systems, but in case of system failures or special circumstances, verbal coordination is required.

Example Scenario: Casablanca (GMMN) to Paris (LFPG)

If the automated system is unavailable, controllers must verbally coordinate all estimates.

  1. Tower reports the departure time to APP.
  2. APP calculates the estimated time at the COP (Coordination Point) between APP and ACC.
  3. APP transmits the estimate to ACC.
Format for Verbal Coordination

APP → ACC:

"ESTIMATE TOLSI AFR123"

ACC → APP:

"A320 to LFPG"

APP → ACC:

"SQUAWKING 6032, ESTIMATED TOLSI 1509, CLIMBING FL150 <initials>"

ACC → APP:

"<initials>"

By confirming the aircraft type and destination, both controllers ensure they are referencing the same flight.

Estimate - No Details

A variation of an Estimate Call is used when the receiving sector has no prior flight plan data for an aircraft.

Additional Details Exchanged

Estimates are not required on VATSIM, as Euroscope automatically exchanges flight data

Expedite Clearance & Revisions

Expedite Clearance

An Expedite Clearance is a short-term coordination request, similar to an Approval Request.

When to Use an Expedite Clearance

Revisions

A Revision is issued when there is a change in the aircraft’s estimated boundary crossing parameters before reaching the sector boundary.

Common Revisions

Revisions are generally unnecessary on VATSIM, as Euroscope automatically updates estimates.
Controllers can monitor changes in real-time without requiring verbal coordination.

Handover-Takeover

structured and informative handover ensures a smooth transition when transferring control of a sector. This is especially critical during high-traffic periods and events, where situational awareness must be maintained.

WEST Principle for Tower Handovers

Category Explanation Examples
W - Weather Any weather conditions that impact operations. "Heavy rain reducing visibility to 2000m," "Wind gusts up to 35 knots from the west," "Moderate turbulence reported at FL120."
E - Equipment Mention any operationally significant equipment issues (rarely relevant on VATSIM). "ILS for Runway 22 out of service," "Transponder issues reported with several aircraft," "Coordination line to adjacent sector is down, using text chat for now."
S - Situation Describe the current operational environment, including staffing, airspace restrictions, or agreements. "Ground and Tower online, Approach offline—providing top-down service," "Runway 18 closed for maintenance," "Holding established for arrivals due to congestion."
T - Traffic List active aircraft and pending actions. "BAW123 cleared for takeoff, waiting for departure separation," "AFR452 holding at FL150 due to traffic," "DLH789 approaching the boundary, handoff required in 2 minutes."

Structuring Approach and Center Handovers

When conducting handover between Approach and Center, follow a general → specific structure:

  1. Basic Information → Area of responsibility, active runways, NOTAMs.
  2. Sector Configuration & Agreements → Which adjacent sectors are online, special coordination agreements.
  3. Traffic Picture → Who is on frequency, their current status, any coordination already completed.
  4. Additional Details → Any reported issues, equipment failures, special operations.

This structured approach helps the incoming controller gradually build an understanding of the traffic picture before assuming control.

Handover Completion Process

RAWFTO Handover Format

Runways
Airspace
Weather
Frequencies
Traffic
Outstanding Instructions / Other Information
Example Handover Exchange
"Runway 35R in use for departures, Runway 35L for arrivals at GMMN. GMME Runway 03 for departure and Runway 21 for arrivals."

"Airspace: GMMM_CTR is online, extending to cover GMMN_APP and GMME_APP. Providing top-down service at GMMN and GMME. No temporary restrictions or closures. Traffic flow normal."

"Weather: Winds 010° at 12 knots, occasional gusts up to 18 knots at GMMN. Visibility 10km, no significant weather affecting arrivals. Cloud cover SCT at 4000 feet, BKN at 10,000 feet. GMME reporting similar conditions with lighter winds at 5 knots from the west."

"Frequencies: 119.10 and 124.75 active. Handoffs to DAAA_CTR for eastbound traffic above FL250."

"Traffic: RAM213 is taxiing for departure from 35L, IFR to LFPG. ATY502 is descending DCT ORSUP, coordination with DAAA_CTR is done. AFR423 is inbound from the north, estimating BARIS in four minutes. LBY112 is climbing out, handoff needed to the next sector. CN-RGB (a VFR flight) is holding at 2000 feet west of the field for sequencing."

"Outstanding: Just frequency transfers and the handoff for LBY112. No conflicts at the moment."

"Any questions?"