Aircraft can be classified according to environmental performance. This report shows there are various classification systems available for the purpose and provides numerous examples of how they might be elaborated. In all cases due knowledge of the features of individual aircraft is first required. The required data on aircraft type, engine type and weight are available from airports. The report was prepared for the Dutch Finance ministry and discussed with the Taskforce on Differentiation of the Air Travel Tax, in which the main stakeholders are represented. The Taskforce was set up following adoption of a motion by Dutch MPs (Parliamentary Proceedings 2007/08, 31 205, no. 45) requesting analysis of the practical scope for relating the country’s air travel tax to the distance flown and the environmental impact of the type of aircraft employed.