Procedures in unusual situations

Emergency procedure

In the event of an emergency, air traffic control applies the so-called “ASSIST” principle. This stands for Acknowledge, Separate, Silence, Inform, Support and Time.


When a pilot reports an emergency, the air traffic controller acknowledges the call. From that moment on, he or she records the aircraft’s position and course so that this data is available as and when needed. 


An aircraft in an emergency situation takes priority over all other traffic and must be able to make an uninterrupted approach to the airfield chosen for its landing. The air traffic controller ensures adequate separation from other traffic.


If radio communication with the aircraft is possible, it is limited to the most essential information. In principle, the air traffic controller only provides the pilot with details he or she specifically asks for. This avoids the pilot, who needs to concentrate upon flying the aircraft, being distracted by useful but non-essential information. Silence gives pilots the time and space they need to focus upon taking the correct action. A separate emergency frequency is available so that the pilot and the controller can communicate one-to-one, without interruptions from other aircraft.


The air traffic controller informs the control tower supervisor of the emergency as quickly as possible, stating the nature of the situation (for example, a technical problem, a hijacking or a bomb warning), what he or she has already done in response and what airfield the pilot has chosen for a precautionary or emergency landing. The pilot is informed of the measures taken in response to the situation.


As far as possible, all requests by the pilot are accepted. For example, he or she may ask to jettison fuel, for specific information (about weather conditions, say, or the plane’s altitude) or to land on a particular runway.


The air traffic controller gives the pilot as much time as possible to deal with the problems on board.


Missing aircraft procedure

When an aircraft fails to arrive at its destination airfield at the expected time, it is listed as missing.

LVNL has a structured procedure for such situations. This is divided into three phases: Uncertainty, Alert and Distress. We provide an “alert service” for every flight using air traffic control services, with a submitted flight plan or otherwise known to us, and for those known or thought to have been hijacked or subject to some other form of so-called “ unlawful interference”. As well as alerting those who come to the aid of an aircraft in distress, such as rescue and policing organisations, we provide them with all necessary assistance.

Phase 1: Uncertainty

The Uncertainty phase begins 30 minutes after air traffic control fails to receive a scheduled call from an aircraft or it does not arrive as expected at its destination airfield, or as soon as an unsuccessful attempt is made to contact it.

Phase 2: Alert

The Alert phase is initiated if attempts to contact the aircraft or to obtain information about it from other sources during the Uncertainty phase are unsuccessful, or if it has been cleared for landing but fails to do so within five minutes of its expected arrival time. This phase is also initiated if LVNL receives information indicating that the aircraft its experiencing problems, but these do not appear serious enough to warrant an emergency landing.

Phase 3: Distress

The Distress phase is initiated if we are still unable to contact the aircraft during the Alert phase and information from other sources suggests that it is in distress. This phase is also initiated if the aircraft would now have run out of fuel, or would not have enough left to land safely, or if air traffic control receives information indicating that it has made or will have to make an emergency landing, or probably has or will have to do so.


In the event of an aircraft accident, or the impending danger of one, at or close to an airfield, LVNL is responsible for alerting its emergency services. All airports and airfields have their own local emergency response procedures, and we have a crisis procedure which can be activated should an incident or some other unusual situation occur.

Reporting procedures

LVNL is required by law to report serious incidents to the Dutch Safety Board (DSB).


The DSB conducts independent investigations into the causes and consequences of disasters, serious accidents and other major incidents, not just in the aviation sector but also in other fields. These exercises highlight lessons to be learnt and result in recommendations to improve safety. Their aim is to learn from such events, not to place blame. When required to do so, it is the LVNL supervisor who notifies the DSB of an incident. The following events must be reported.


Emergency situations (“Mayday” calls).


Collisions and near-collisions (loss of separation) between aircraft.


Collisions and near-collisions between aircraft and obstacles on the ground.


Take-offs or attempted take-offs from an out-of-use or occupied runway, or from one not authorised for take-off by air traffic control.


Landings or attempted landings on an out-of-use or occupied runway, or from one not authorised for landing by air traffic control.


Runway excursions during take-off or landing.


Runway incursions with actual or potential risk of collision.


The DSB decides whether or not to begin an investigation within five days of receiving notification from LVNL.


Under the statutory Civil Aviation Incident Notification Order (Besluit melding voorvallen in de burgerluchtvaart), both LVNL as an organisation and its air traffic controllers as individuals are also required to report incidents related to the provision of air traffic control services to the Aviation Incidents Analysis Bureau (Analysebureau Luchtvaartvoorvallen) at the Human Environment and Transport Inspectorate (Inspectie voor Leefomgeving en Transport, ILT). Again, the aim is to draw lessons from these events.