Categories of messages

Table of Contents

Message Priority Table

The categories of messages handled by the aeronautical mobile service and the order of priority in the establishment of communications and the transmission of messages shall be in accordance with the following table.

Message category and order of priorityRadiotelephony signal
a) Distress calls, distress messages and distress trafficMAYDAY
b) Urgency messages, including messages preceded by the medical transports signalPAN, PAN or PAN, PAN MEDICAL
c) Communications relating to direction finding–
d) Flight safety messages–
e) Meteorological messages–
f) Flight regularity messages–

Unlawful Interference Note

Note 1 Messages concerning acts of unlawful interference constitute a case of exceptional circumstances which may preclude the use of recognized communication procedures used to determine message category and priority.

NOTAM Priority Decision

Note 2 A NOTAM may qualify for any of the categories or priorities c) to f) inclusive. The decision as to which priority will depend on the contents of the NOTAM and its importance to the aircraft concerned.

Distress and Urgency Messages

5.1.8.1 Distress messages and distress traffic shall be handled in accordance with the provisions of 5.3.

Training reference only. Always defer to current approved manuals and official procedures.

5.1.8.2 Urgency messages and urgency traffic, including messages preceded by the medical transports signal, shall be handled in accordance with the provisions of 5.3.

Note The term “medical transports” is defined in the 1949 Geneva Conventions and Additional Protocols (see also RR S33 Section III) and refers to “any means of transportation by land, water, or air, whether military or civilian, permanent or temporary, assigned exclusively to medical transportation and under the control of a competent authority of a Party to the conflict”.

Direction Finding Communications

5.1.8.3 Communications relating to direction finding shall be handled in accordance with Chapter 6 (Aeronautical Radio Navigation Service).

Flight Safety Messages

5.1.8.4 Flight safety messages shall comprise the following:

  1. movement and control messages [see PANS-ATM (Doc 4444)];
  2. messages originated by an aircraft operating agency or by an aircraft, of immediate concern to an aircraft in flight;
  3. meteorological advice of immediate concern to an aircraft in flight or about to depart (individually communicated or for broadcast);
  4. other messages concerning aircraft in flight or about to depart.

Meteorological Messages

5.1.8.5 Meteorological messages shall comprise meteorological information to or from aircraft, other than those in 5.1.8.4, 3).

Flight Regularity Messages

5.1.8.6 Flight regularity messages shall comprise the following:

  1. messages regarding the operation or maintenance of facilities essential for the safety or regularity of aircraft operation;
  2. messages concerning the servicing of aircraft;
  3. instructions to aircraft operating agency representatives concerning changes in requirements for passengers and crew caused by unavoidable deviations from normal operating schedules. Individual requirements of passengers or crew shall not be admissible in this type of message;
  4. messages concerning non-routine landings to be made by the aircraft;
  5. messages concerning aircraft parts and materials urgently required;
  6. messages concerning changes in aircraft operating schedules.

ATC Unit Limitations

5.1.8.6.1 Air traffic services units using direct pilot- controller communication channels shall only be required to handle flight regularity messages provided this can be achieved without interference with their primary role and no other channels are available for the handling of such messages.

Note The messages at 5.1.8.4, 2) and 5.1.8.6, 1) to 6) typify some of the operational control communications defined in Chapter 1.

Transmission Order Recommendation

5.1.8.7 Recommendation. Messages having the same priority should, in general, be transmitted in the order in which they are received for transmission.

Interpilot Air-to-Air Communication

5.1.8.8 Interpilot air-to-air communication shall comprise messages related to any matter affecting safety and regularity of flight. The category and priority of these messages shall be determined on the basis of their content in accordance with 5.1.8.