## 6 Discussion/Conclusions  
The research presented in this paper uses multi-criteria analysis of the level of service for low-cost carriers with the aim of defining criteria that will enable a more comprehensive assessment and upgrade of the existing system (IATA LOS guidelines), and their objective ranking, taking into account the main influential factors (price, time, and space). The assessment of the observed system (LCCs), which aims to establish the optimal LOS for LCCs, is based on determining the main criteria for their evaluation with multi-criteria analysis and comparison of the importance of individual factors in specific conditions within the passenger flow. Most airports today use the IATA LOS methodology. The aforementioned methodology is used for determining the level of service (LOS) at the airport terminal facilities, and it is primarily based on the business model of traditional full-service airlines. Given that low-cost carriers are increasingly present at airports today, there is a need to design passenger terminal facilities in compliance with the growing segment of LCCs. This type of airlinebusiness model has different requirements and preferences, and it is important to recognize them in order to adjust the current LOS guidelines. The conducted analysis enabled a deeper understanding of passenger needs, which contributed to creating a complete view of the characteristics of LCC passengers. The basic conclusion that emerged from the analysis is that passengers using the services of low-cost carriers are willing to wait longer and have less available space per passenger for a lower price. This dictates the need to establish new LOS parameters that will meet passenger requirements and increase operational efficiency. Therefore, defining new LOS guidelines and their implementation at airports is imperative because it can increase the efficiency of the passenger terminal. Hence, the spatial-temporal parameters (waiting times, space per passenger, and occupancy of facilities) should be adapted to the specificities of different airline business models, i.e., low-cost carriers in this case. The methods of survey questionnaire and analytical hierarchical process (AHP) in the airport were used for the purpose of exploring the functional efficiency and level of service at the airports. Based on the obtained results via survey questionnaires, an analysis of the level of service (LOS) at the airport terminal facilities for low-cost carriers (LCCs) was conducted, and a hierarchical AHP decision-making model was developed. Finally, by using AHP model, new spatial-temporal parameters for the optimal level of service (LOS) for low-cost carriers (LCCs) were proposed, developed, and presented. The significance of this study is emphasized in achieving greater efficiency of the passenger terminal in accordance with the requirements of low-cost carriers. The proposed research includes the establishment of LOS guidelines for low-cost carriers in accordance with their requirements. The scientific contribution is reflected in the definition of the new level of service guidelines adapted for low-cost airlines whose needs in terms of spatial and time requirements differ from traditional full-service network carriers. The new guidelines cover all main airport terminal facilities, taking into account the perception of the service obtained from passengers through a survey and the results confirmed by multi-criteria analysis of the optimal LOS for low-cost airlines. A new range of optimal LOS values for LCCs within the passenger flow has been defined. The new guidelines will lead to the better utilization of airport terminal facilities. Citing waiting time as an example, the majority of passengers expressed their willingness to accept a lower level of service within the passenger terminal for a lower price. More than half of them (57.3%) are willing to wait longer and be in a crowd when waiting in line if they pay a lower ticket price in return.