The insurance requirements are set up by EC 785/2004 Regulation. The amount varies depending on the maximum take-off weight of the aircraft and the maximum number of passengers carried.
From a legal point of view, each and every flight has to be insured for their aviation-specific liability in respect of passengers and third parties. The insured risks shall include acts of war, terrorism, hijacking, acts of sabotage, unlawful,seizure of aircraft and civil commotion.
If you opt for the pilot-attached formula, you will have your liability insurance covered on any aircraft belonging to an ILAS member, subject to the MTOW and the maximum number of passengers declared in your insurance policy.