A data processing system is disclosed which tracks each client's cumulative travel usage over time for the purpose of authorizing travel requests and ensuring a predetermined minimum return on an initial investment base. Such variables as frequency of use and level of service (i.e., first class, coach,...http://www.google.co.uk/patents/US4885685?utm_source=gb-gplus-sharePatent US4885685 - Investment management system with travel usage funds indexed to customer account status
