Due to the increasing importance of customer orientation to a competitive advantage, airport managers emphasise passengers' perceptions and expectations of airport services quality. This paper aims to develop a multi-criteria evaluation model to evaluate the gap between passengers' perceptions (perceived service quality) and their expectations (expected service quality), and to diagnose managerial strategies of gap reduction within the airport passenger service context. This multi-criteria evaluation model is combined with the analytic hierarchy process method, the VIKOR (VIsekriterijumska optimizacija i KOmpromisno Resenje in Serbian, which means Multicriteria Optimization and Compromise Solution) method, and the importance-performance analysis (IPA) technique. The multi-criteria model can not only overcome the weaknesses of traditional IPA, it can also consider passenger preferences and satisfaction simultaneously to analyse managerial strategies for reducing the customer gap, thus improving service quality and meeting passengers' expectations. This paper also provides an empirical case study of passenger services at Taoyuan International Airport in Taiwan, demonstrating the suitability and effectiveness of the multi-criteria evaluation model.