The risk – The amount of revenue and profit recognised in a year on the sale of engines and aftermarket services is dependent, inter alia, on the assessment of the percentage of completion of long-term aftermarket contracts and the forecast cost profile of each arrangement. As long-term aftermarket contracts can extend over significant periods and the profitability of these arrangements typically assumes significant life-cycle cost improvement over the term of the contracts, the estimated outturn requires significant judgement to be applied in assessing engine flying hours, time on wing and other operating parameters, the pattern of future maintenance activity and the costs to be incurred. The inherent nature of these estimates means that their continual refinement can have an impact on the profits of the Civil aerospace business that can be significant in an individual financial year. The assessment of the estimated outturn for each arrangement involves detailed calculations using large and complex databases with a significant level of manual intervention