. Because most reservations systems and, in turn, third-generation RM systems were developed on the basis of leg/fare class data, most airlines did not have access to the detailed historical ODIF booking data required by network optimization models
. Because most reservations systemsand, in turn, third-generation RM systems weredeveloped on the basis of leg/fare class data, mostairlines did not have access to the detailed historicalODIF booking data required by network optimizationmodels