Liability in Automated Systems

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Liability in Automated Systems

33RD ANNUAL CONFERENCE, Ottawa, Canada, 18-22 April 1994

WP No. 143

Liability in Automated Systems



During the 30th Annual Conference in Trinidad, Conference accepted the recommendations of a Standing Committee 4 Working Paper on Automation and the air traffic controller in as much as the legal aspects of a controller’s responsibilities in respect of automated systems should be clearly defined.

Following the presentation of a paper on this subject to the 32nd annual Conference in Christchurch, New Zealand, further work in this area was requested by Committee C and Standing Committee 1.


Standing Committee 4 have been tasked to address the following areas of concern:

i) When an aircraft initiating a manoeuvre as a result of a Resolution Advisory issued by an automated system, loses separation with other traffic to the extent that a serious incident/accident occurs;

ii) When an aircraft as a result of the “Domino Effect” is involved in an incident/accident with another aircraft;

iii) A pilot does not comply with ATC clearance until he is satisfied that based on Airborne Collision Avoidance System (ACAS) information it is safe to do so, resulting in an incident/accident occurring due to the delayed action;

iv) Recovery of the situation when an automated ATC system fails.

Items i) and ii) are covered by the existing IFATCA Policy agreed in New Zealand:

“A controller shall not be held liable for incidents in which a loss of separation occurs due to a resolution advisory issued by an automated system “

(IFATCA Policy Manual, Page 4412, para. 1.11)

It is very difficult if not impossible to give a straightforward legal answer as to who is liable in the above situations. It always depends on the specific details of the case in question. Investigations in the United Kingdom have indicated that as long as the controller concerned deals with the situation to the best of his ability, then they cannot be held liable for any resulting incidents that may occur. Liability only becomes possible if negligence can be proved. This does not of course prevent injured parties from trying to apportion blame.

In relation to item iii) above, a controller can only provide a safe and expeditious flow of traffic if aircraft under his control comply promptly and accurately with any Air Traffic Control clearance issued to them. It must emphasized that when a pilot does not follow these rules, responsibility for the safe operation of the aircraft concerned from other traffic operating in the same or adjacent airspace must pass directly to the pilot in command.

Regarding item iv) above, Member Associations should actively encourage the development of guidelines and procedures to deal with the recovery of the situation in the event of automated systems failure. In order that the effect of any system breakdown is kept to minimum, backup systems should be provided. In addition it may be necessary for specific techniques to be developed to aid detection of any system failure, and to assist the re-introduction of the automated system once the fault has been rectified.


In order that incidents caused by automated systems are kept to an absolute minimum, it is essential that all automated Air Traffic Control Systems incorporate verification controls to guarantee that the data supplied is correct and fail-safe.

Provision of back-up ATC systems is a fundamental requirement to ensure that any failure of one part of such system does not affect the integrity of the Air Traffic Control Service being provided.

Member Associations should seek to ensure that the operational use of ACAS is agreed with the appropriate air traffic control authorities before the system is brought into service.


A controller shall not be held liable for any incident resulting from the failure of an automated air traffic control system.

Guidelines and procedures shall be established in order to prevent incidents arising from the use of false or misleading information provided by ACAS.

Last Update: September 20, 2020  

December 23, 2019   249   Jean-Francois Lepage    1994    

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