## 5 Proposal of New Spatial-Temporal Parameters for Optimal Level of Service for Low-Cost Carriers  
In this research, the focus was determining new spatial-temporal parameters for the optimal level of service (LOS) for low-cost carriers (LCCs). A survey questionnaire regarding passengers' attitudes on the airport terminal facilities services received within the airport passenger terminal from the moment they arrive at the terminal to the moment they board the aircraft was collected. Based on the obtained results, an analysis of the level of service (LOS) at the airport terminal facilities for low-cost carriers (LCCs) was conducted, and an AHP decision-making model was developed to determine new spatial-temporal parameters for the optimal level of service (LOS) for low-cost carriers (LCCs). The proposal of new LOS guidelines with new spatial-temporal parameters for the optimal LOS for LCCs is presented in Table 5.  
The aim of this research was to determine the optimal level of service (LOS) for low-cost carriers (LCCs). This was conducted using a survey questionnaire regarding passengers' attitudes on the services received within the airport passenger terminal from the moment they arrive at the terminal to the moment they board the aircraft. All main airport terminal facilities and their perception of the service in them were covered. The survey was aimed at respondents (passengers) who frequently use the services of low-cost carriers. A total of 68 questionnaires were completed anonymously. All collected responses were analyzed, and the following conclusions were reached, which have an impact on the establishment of new spatial-temporal parameters for the optimal level of service (LOS) for low-cost carriers (LCCs). The main criterion by which passengers choose an airline is price (82.4%). The main indicator that influences the level of service within the passenger terminal is the time spent waiting in line (67.6%). When waiting in line, the available space has a major impact on the perception of service quality in the passenger terminal (61.6%). The majority of passengers would accept a lower level of service (longer waiting time, less available space) for a more favorable ticket price (57.3%). The majority of passengers are willing to wait for check-in more than 20 min (75%) if they pay a lower price for the flight ticket. More than half of passengers (52.5%) are willing to wait longer for other services if they pay less for the flight ticket. The optimal waiting times have increased while spatial parameters have been reduced in accordance with the preferences of passengers using LCC services. In line with this, it is possible to more efficiently utilize airport terminal facilities and enhance the functional efficiency of a passenger terminal with a dominant share of this business model. Further, the majority of passengers (83.8%) are willing to use self-service kiosks and online check-in for a flight. The most common reasons for avoiding the use of self-service technology are the following: feeling of frustration when using technologies, technical problems, unforeseen difficulties, and lack of support in case of problems. Most passengers (80%) are ready to use mobile applications for the purpose of a better experience of passing through the passenger terminal. By establishing new LOS parameters for LCCs, it is possible to model the capacity and level of service of the airport passenger terminal, to assess new requirements (greenfield investment) for airport terminal facilities, and to calculate the current state (LOS) of airport terminal facilities by adopting new LCC parameters. By comparing the IATA LOS guidelines (see Table 1) with the new LOS guidelines developed for LCC needs (Table 5), the following savings were proposed: for the check-in segment, 0.3 m\({}^{2}\)/passenger; and for security control and immigration/emigration control, a reduction of 0.2 m\({}^{2}\)/passenger.