Emergency basics[PDF]


The procedures outlined herein are intended as a general guide to air traffic services personnel. Air traffic control units shall maintain full and complete coordination, and personnel shall use their best judgment in handling emergency situations.

Squawk code during emergency

If the pilot of an aircraft encountering a state of emergency has previously been directed by ATC to operate the transponder on a specific code, this code will normally be maintained until the pilot has been advised otherwise. However, the fact that the pilot squawks on 7700 helps the coordination between controllers. This does not apply to urgency calls.

Distress signals

The following signals, used either together or separately, mean that grave and imminent danger threatens, and immediate assistance is requested:

  • a signal made by radiotelegraphy or by any other signalling method consisting of the group SOS (. . . — — — . . . in the Morse Code)
  • a radio telephony distress signal consisting of the spoken word MAYDAY
  • a distress message sent via data link which transmits the intent of the word MAYDAY
  • rockets or shells throwing red lights, fired one at a time at short intervals
  • a parachute flare showing a red light

Urgency signals

The following signals, used either together or separately, mean that an aircraft wishes to give notice of difficulties which compel it to land without requiring immediate assistance:

  • the repeated switching on and off of the landing lights
  • the repeated switching on and off of the navigation lights in such manner as to be distinct from flashing navigation lights.

The following signals, used either together or separately, mean that an aircraft has a very urgent message to transmit concerning the safety of a ship, aircraft or other vehicle, or of some person on board or within sight:

  • a signal made by radiotelegraphy or by any other signalling method consisting of the group XXX ( — . . — x3)
  • a radio telephony urgency signal consisting of the spoken words PAN, PAN
  • an urgency message sent via data link which transmits the intent of the words PAN, PAN.

Emergency declaration by voice

Urgency call (PAN-PAN)

A pilot will declare an urgency call by using the spoken words PAN PAN (3x) followed by his message when he is in a condition concerning the safety of the aircraft or some person on board, but which does not require immediate assistance.
Urgency calls take priority over all other messages, except distress calls. As an active controller, you shall acknowledge the urgency call — ATC: [aircraft Call sign] Roger PAN PAN at time [hhmm]Z.

There is no need to give the aircraft absolute priority. However an expeditious ATC service is required. Usually a pilot will let you know if he requires anything from you. If not given, you can try to get any information you think is necessary to enable you giving the pilot the best service possible.
A pilot may tell you to standby, because he is busy or doesn’t have an answer to your question just yet. But you can trust that he will get back to you when he can.
How to handle an urgency call will be different every time. There are some aspects which are Important to remember, for instance:

  • Do not get tunnel vision and do not focus solely on the traffic requiring assistance.
  • Do not stop controlling as you may still have other traffic requiring your attention.
  • There is no need to get stressed. Stay calm, you are not the one having problems. A calm controller, who sounds in control of the situation, reassures the pilot(s).
  • Make sure you inform your adjacent controllers of the situation. Relay any information that could be of value to them.
Manoeuvring instructions to an aircraft experiencing engine failure should be limited to a minimum. For instance, climb instructions shall be avoided or suitable to the performance of the airplane.

Distress cal (MAYDAY)

A pilot will issue a distress call by using the words MAYDAY (3x) followed by his message when he is in a condition of being threatened by serious and/or imminent danger and of requiring immediate assistance.
Distress calls take priority over all other messages. As controller you shall acknowledge the distress call — ATC: [aircraft Call sign] Roger MAY DAY at time [hhmm]Z. When a MAYDAY is declared the aircraft requires an absolute priority service over all the other traffic.
When appropriate, other aircraft operating in the vicinity of the aircraft in emergency should be advised of the circumstances. Regarding the interaction ATC-crew, the same basic principles regarding the communications and instructions of an urgency call aply.

Emergency handling


When an emergency is declared by an aircraft, the ATS unit should take appropriate and relevant action as follows:

  1. Unless clearly stated by the flight crew, take all necessary steps to ascertain aircraft identification and type, the type of emergency, the intentions of the flight crew as well as the position and level of the aircraft.
  2. Decide upon the most appropriate type of assistance which can be rendered.
  3. Enlist the aid of any other ATS unit or other services which may be able to provide assistance to the aircraft.
  4. Provide the flight crew with any information requested as well as any additional relevant information, such as details on suitable aerodromes, minimum safe altitudes, weather information.
  5. Obtain from the operator or the flight crew such of the following information as may be relevant (number of people on board, amount of fuel remaining, possible hazardous materials – these items could not be taken into account for IVAO as we are speaking about virtual flight).
  6. Notify nearby appropriate air traffic service units.
An aircraft known or believed to be in a state of emergency, including being subjected to unlawful interference shall be given priority over other aircraft.

Checklist ASSIST

ASSIST is a simple set of acronyms which may make it easier for controllers to remember the immediate actions, or sequence of actions, to be followed on initial notification in event of unusual/emergency situation:

  • Acknowledge the call.
  • Separate the aircraft from other traffic. Give it room to manoeuvre.
  • Silence on the frequency. Provide separate frequency where possible - this prevents unnecessary clutter for the pilots.
  • Inform those who need to know and those who can help; inform others as appropriate.
  • Support the pilots in any way possible - start thinking of alternative routings, etc.
  • Time. Give the pilots time to collect their thoughts, don’t harass them for information. Time leads to good decisions.

Many organizations successfully adopted the ASSIST principle pioneered by the Deutsche Flugsicherung GmbH (DFS) entrusted for controlling the air traffic in Germany.

Specific cases

Emergency descent

Upon receipt of advice that an aircraft is making an emergency descent through other traffic, all possible actions shall be taken immediately to safeguard all aircraft concerned.
The air traffic controller concerned shall inform any other air traffic controllers and control sectors which may be affected.

Immediately after such an emergency broadcast has been made, the approach control unit or the aerodrome control tower concerned shall forward further clearances to all aircraft involved as to additional procedures to be followed during and subsequent to the emergency descent.

Weather deviation

When pilot initiates communication with ATC, a rapid response may be obtained by stating WEATHER DEVIATION REQUIRED to indicate that priority is desired on the frequency and for ATC response.

When necessary, the pilot shall upgrade the situation to the urgency status.
The pilot shall inform ATC when weather deviation is no longer required, or when a weather deviation has been completed and the aircraft has returned to its cleared route.
ATC should take one of the following actions:

  • When appropriate separation can be applied, issue clearance to deviate from track.
  • If there is conflicting traffic and ATC is unable to establish appropriate separation, ATC shall:
    • Advise the pilot of inability to issue clearance for the requested deviation, and
    • Advise the pilot of conflicting traffic, and
    • Request the pilot’s intention

See also


  • ICAO documentation Annex 2 - Rules of the Air - 10th Edition July 2005


  • VID 150259 - Creation
  • VID 435695 - Wiki integration
  • VID 150259 - Update September 2019


  • 16:48, 15 November 2019


  • This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.


  • The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.