This paper quantified the impact of outbound and return flight schedule preferences on airline choice for international trips. Several studies have used airline choice data to identify preferences and trade-offs of different air carrier service attributes, such as travel time, fare and frequencies. However, estimation of the effect return flight schedules have on airline choice for an international round-trip flight has not yet been studied in detail. Therefore, we developed a stated preference survey that includes round-trip fares based on flight schedule combinations and the number of days prior to departure fares was purchased. We applied modelling techniques using a set of stated preference data. A mixed logit model was tested for the presence of heterogeneity in passengers preferences. Our results indicated that return flight schedule preference plays a substantial role in air carrier choice and has a similar effect to outbound flight schedule preference. Willingness to pay and a sensitivity analysis of airline service characteristics and their marketing implications are conducted. Outputs show that travellers are willing to pay more to reduce the difference between preferred schedule time and the schedule provided by the airline. This paper highlights the importance of exploring airline choice behaviours considering attributes of both the outbound and return trips to develop effective operational and marketing strategies for the international air travel market