Barkingmad, thanks for referring me to p161/162 of the N571UP final report. The figures mentioned are all part of the statistical measurement of risk data. Risks for all airlines have to be quantified, measurements have to be made, data described and forecasts made and anyone involved in insurance cannot escape the need to use such numbers. Based on this an appropriate insurance premium is charged and cover provided. Insurance is based on the possibility of an event happening within the period of cover. If the event was a certainty then it probably wouldn't be insurable.