Description

The purpose of a Letter of Agreement (LoA) between two ATS units is to define the coordination procedures to be applied between these units. The procedures described in the LoA are supplementary to ICAO SARPs, as well as to those specified in national and international legislation.

Normally, LoA content is very detailed and the procedures are tailored to the needs of particular situations that arise during coordination between the particular ATS units.

Guidance provided by ICAO is limited. Doc 9426 recommends that important ATS matters between neighbouring States are described in formal LoAs between the States and the relevant ATS units. The document also includes an LoA example but does not imply this is the only acceptable format.

LoAs exist not only between ATS units in neighbouring States but also between different facilities in the same State. Normally, when two or more ATS units are co-located (for example, an Approach control unit and an Aerodrome control tower), the coordination procedures are described in an Operations manual or similar document. If the ATS units are located at different facilities (e.g. an ACC and several APPs or TWRs), this can be arranged either through an LoA or an Operations manual, depending on the circumstances and the ANSP procedures.

To facilitate harmonization, common formats are developed, though not universally applicable. Examples of these are the EUROCONTROL common format and the FAA LoA format.

In Europe, the EUROCONTROL Common Format is used. This allows users (e.g. air traffic controllers, engineers, etc.) to quickly find the information they need. The common format LoA covers all aspects of inter-unit coordination and comprises a main body and annexes. The main body contains the following sections:

• General, containing a brief description of the LoA subject matter, e.g. type of traffic it applies to (e.g. IFR/VFR/GAT/OAT)
• Areas of Responsibility and Delegation of the Responsibility for the Provision of ATS
• Procedures (a list of Annexes)
• Revisions and Deviations (procedures for amendment or deviation from the standard provisions)
• Cancellation
• Interpretation and settlement of disputes
• Validity
• Appendices with maps describing Delegations of ATS (if applicable)

The main body of the LoA defines the general framework of the agreement. The detailed procedures are specified in the Annexes:

• Annex A. Definitions and Abbreviations
• Annex B. Area of Common Interest. This Annex contains a definition of the area of common interest (the area on both sides along the border between the areas of responsibility of the two units for which everyone concerned must be sufficiently knowledgeable about the neighbouring airspace). This annex includes maps and tables describing various airspace elements (waypoints, airways, FRA, SUAs, sectorization, etc.).
• Annex C. Exchange of Flight Data. This Annex is divided into two subparts (automatic and verbal). Both contain description of the respective equipment being used (e.g. data links, landlines, sat phones, etc.) as well as fallback procedures in case of equipment failure.
  • Annex C1. Exchange of Flight Data (Automatic). This Annex describes the exchange of OLDI messages.
  • Annex C2. Exchange of Flight Data (Verbal). This Annex describes the procedures for voice exchanges of flight data such as estimates (content and time frame), revisions, approval requests, etc.).
• Annex D. Procedures for Coordination. This Annex describes the general coordination procedures such as:
  • Level allocation for general purposes and for specific situations (e.g. aerodromes near the border, flights crossing at specific points, etc.).
  • Coordination for VFR flights
  • Coordination of the status of SUAs in the area of common interest
• Annex E. Transfer of Control and Transfer of Communication
• Annex F. ATS Surveillance Based Coordination Procedures. This Annex contains procedures for transfer of identification, conditions for transfer of control (e.g. if a set of criteria are met, the aircraft can be handed over without the need to coordinate each transfer separately).
• Annex G. Supplementary Procedures. This Annex is optional and is used to describe procedures that do not fit in the previous Annexes. Examples of such procedures include Low Visibility Procedures, Contingency Plans, planning and coordination of special events, etc.
• Annex H. Checklist of Pages. This Annex is optional and contains a tabular view of all the document pages together with their respective validity dates. 

In the USA, the LoA format is described in Order JO 7210.3 Facility Operation and Administration (link in Further Reading below). LoAs are negotiated if the air traffic manager deems it necessary to clarify responsibilities of other persons/facilities/organizations when specific operational/procedural needs require their cooperation and concurrence. Unlike the EUROCONTROL model, each and every aspect is subject to a separate LoA, thus the documents are smaller in size but greater in number. Each LoA contains the following elements:

• Subject
• Purpose 
• Scope 
• Responsibilities
• Procedures
• Attachments (e.g. charts)

Related Articles

• How Air Traffic Control Works
• Coordination in ATM
• ATS Unit Coordination

Further Reading

• ICAO Doc 9426: ATS Planning Manual, Part II, Section 1, Chapter 2: Coordination
• EUROCONTROL Common Format LoA between ATS Units
• Order JO 7210.3 - Facility Operation and Administration