The implications of travel time uncertainty on the operational efficiency of airport terminals have until now not been examined. With the forecast growth in congestion levels predicted for all modes of transport, not only will travel time uncertainty increase but its impact may increase also. The first part of this thesis covers the analysis of two passenger surveys conducted at Manchester Airport and Birmingham Airport. These surveys had the objective of providing evidence to support or dispute the belief that air travellers react to travel time uncertainty. The research identifies that passengers do react by allowing margins of safety for their access journeys, and that this change in behaviour will modify the arrival distribution patterns at airports. The second part of this thesis examines how airport passenger flows could be altered by a change in the arrival distribution of originating passengers at airport terminals. Three airports - Manchester, Birmingham and East Midlands International - are modelled using a simulation tool and tested to assess how a shift in arrival distribution affects queuing and peak passenger volumes within the airport terminal. The findings of this thesis show that airport passenger terminal operational efficiency is affected by access journey time uncertainty. It also identifies that passenger decision making can only be explained by various combinations of factors. Possible methods of minimising the effects of travel time uncertainty are considered. The advantages and disadvantages of access journey time uncertainty for airports and airlines are discussed. It concludes that, to be successful in overcoming negative aspects, both parties must provide a service that results in customer satisfaction. This is the only sure way to maintain their respective revenue levels and secure their future in what is becoming an increasingly competitive industry.