The Chief Inspector of Air Accidents has the power under The Civil Aviation (Investigation of Air Accidents and Incidents) Regulations 2018 to investigate any aircraft incident he sees fit if he thinks there safety lessons to be drawn from it, whether it meets the ICAO accident/serious incident definitions or not. The Ethiopia B787 lithium battery fire at Heathrow in 2013 was one such event - vacant aircraft, stationary, not being prepared for flight, no injuries, no statutory requirement for an investigation, but findings that grounded the whole fleet while a fix was found.