During the present ICAO three-year cycle, an Ad hoc Working Group of the ICAO Council and MBM experts assessed options for MBMs, including design features and a quantitative review. The analysis determined that MBMs based on purchase of carbon credits from outside the sector can contribute to achieving the CNG2020 goal at a relatively low cost compared to the cost of in-sector reductions and with marginal differences between regions and groups of states. The costs of MBM application as assessed would have very limited impact on airline economics. Using a carbon price of US$3 and the most optimistic technology and operational improvements, MBM cost as a proportion of revenue would not represent more than US$0.40 per passenger on a long-haul flight and US$0.10 on a short-haul flight. At the other end of the spectrum, a carbon price up to US$45 and low technology and operational improvements would add US$7.60 to a long-haul flight and US$2.30 on a short-haul flight (ICAO 2013b).