The UK Defence Accident Investigation Branch (Defence AIB) (formerly Military Air Accident Investigation Branch (MilAAIB)) is part of the UK Military Aviation Authority (MAA) which, since 1 April 2015, has itself been part of the UK Defence Safety Authority. The MAA provides the Convening Authority for an aviation-related Service Inquiry (SI). Air accident and incident investigations involving military-registered aircraft are undertaken by the Defence AIB and a Service Inquiry Panel working together as a team led by the appointed President of the SI Panel. Where the matters under investigation involve the function of the MAA, the SI President must report directly to the Permanent Under Secretary at the UK Ministry of Defence (MoD) who is the senior civil servant at the MoD.
The Defence AIB has a Head and Deputy Head and a team of engineering and operations investigators. It is provided with administrative accommodation by the AAIB. A formal agreement between the two agencies provides for an AAIB advisor to assist the Defence AIB Team in support of an aviation SI. In the case of civil/military accidents, a parallel investigation would normally occur with the publication of investigative findings coordinated and concurrent publication considered. In the case of civil aircraft accidents at military aerodromes, the AAIB would lead the investigation with Defence AIB support whereas in the case of military aircraft accidents at civil aerodromes, the Defence AIB would normally lead the investigation and the AAIB would provide support on request.
SI Panel Reports of Investigations are submitted to the Convening Authority as Provisional Reports and after review and the addition of comments by the Convening Authority are published with the status of Final Reports.