Spanish Regulations
Title II of Act 21/2003 of 7 July on Aviation Safety (published in the B.O.E. of 8 July 2003) regulates the technical investigation of civil aviation accidents and incidents. As indicated in its introduction, this Act reinforces the independence of the Civil Aviation Accidents and Incidents Investigation Commission, the body responsible for investigations, which is a constituent part of the Ministerio de Fomento.
It also grants specific legal status to the investigative function for the purpose of preserving its true objective, which consists of determining the cause of civil aviation accidents and incidents and improving aviation safety, but not of establishing blame or responsibility for them. Lastly, it emphasises the confidential nature of the information used in the investigations.
In the same line as other legal provisions of the Act, a system of penalties is established for serious or very serious violations relating to accident investigations (such as, for example, failure to comply with the obligations to communicate and preserve the confidentiality of the information, hindering or obstructing the investigations, falsifying, concealing, altering or destroying records, documents or data, etc.).
Ley 21/2003 
Law 21/2003
Previous legislation includes Act 48/1960 of 21 July on aerial navigation, whose article 134 covers the investigation of aviation accidents and establishes that it is the responsibility of the aeronautical authorities to conduct investigations in the case of accidents.
This Act was extended by the passing of Decree 959/1974 of 28 March on the investigation and reporting of civil aviation accidents, which, as a constituent part of the Undersecretary's Office for Civil Aviation, created the Civil Aviation Accidents and Incidents Investigation Commission as a body of specialists responsible for assignments of a technical nature, devoid of any legal character.
Royal Decree 389/1998of 13 March 1998, regulating the investigation of civil aviation accidents and incidents (B.O.E. of 23 March 1998), incorporated European Council Directive 94/56/EC into Spanish law, updated the investigation procedure, and established the functions of the various components of the Commission according to the new organisational framework of the General State Administration. This basically involved a change in the affiliation and composition of the Plenary Board, which henceforth became known as the Civil Aviation Accidents and Incidents Investigation Commission, and also granted the investigators a status which would enable them to carry out their functions freely and using independent judgement.
International Regulations
I.C.A.O.
The investigation of civil aviation accidents, as a necessary and useful method for improving aviation safety by preventing such accidents, is regulated at the international level by the Convention on international civil aviation signed in Chicago on 7 December 1944, which created the International Civil Aviation Organisation (I.C.A.O.), accountable to the United Nations Organisation, and particularly to the specifications of articles 26 and 37.
As a result of this, on 11 April 1951 the Council of the I.C.A.O. adopted the Standards and Recommended Practices for Aircraft Accident Inquiries, designated as Annex 13 to the Convention.
Over time, Annex 13 to the Convention has undergone a number of modifications and is now known as the Investigation of Aviation Accidents and Incidents.
This Convention regulates the notification of accidents and incidents, the constitution, organisation and conducting of the investigation, participation in the investigation, the presentation and publication of its results, and a series of activities aimed at encouraging the prevention of accidents.
EUROPEAN UNION
At the European Union level, “Council Directive 94/56/EC of 21 November 1994 establishing the fundamental principles governing the investigation of civil aviation accidents and incidents” is currently in force, and establishes a common regulation in line with Annex 13 of the I.C.A.O. for all the member States.
The fundamental aspects of this directive include:
- Each member State is responsible for ensuring that the technical investigations are carried out by a permanent civil aeronautical body or entity or monitored by such body or entity.
- This body or entity must be independent from the functional point of view, particularly of any organisation related to the aeronautical industry.
- It establishes cooperation mechanisms between the member States.
Directiva 94/56/CE 
Council Directive 94/56/CE
