## 3 Materials and Methods
### Data Collection  
In general, surveys can be conducted in person, by phone, online, or by mail, depending on the research objectives and characteristics of the population being studied. When the survey is conducted online, different platforms can be used. The survey design for this research was conducted online using a Google Docs form. The survey was shared with the target group of respondents (passengers/travelers) via email, social media, and other online platforms. The time period from starting the survey to the end of the survey was one month, which was also enough time to provide feedback. After a month, the responses were collected and the results (attitudes and opinions of the respondents) were analyzed, based on which conclusions were drawn. The survey was conducted anonymously in early 2024, 200 requests were sent out, and a total of 68 completed questionnaires were collected. It took an average of 10 min to complete the survey.  
Key aspects of conducting an online survey include selecting the appropriate tool (platform), clearly defining the questions, adjusting the survey settings, effectively sharing the survey with the target group, and analyzing the results to obtain the required information. The questions for the target group (passengers) were designed to provide answers and opinions on the services received within the 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 on them were covered.  
The aforementioned methodology, i.e., a survey, enables a deeper understanding of passenger needs and contributes to creating a comprehensive picture of the characteristics of LCC passengers. Based on the survey, a multi-criteria analysis of the optimal LOS for LCCs was performed, which aims to define criteria that will enable a more comprehensive assessment and upgrade of the existing system (IATA LOS guidelines), as well as their objective ranking, taking into account the main influencing factors (price, time, and space).  
The survey was divided into two groups of questions (I and II). The first segment of the survey (group of questions I) consists of general questions and includes a total of 21 questions, and the second segment (group of questions II) consists of 9 questions. In the second group of questions, it is necessary to compare two concepts with each other (first-mentioned and second-mentioned), where the following apply: 1--equal importance; 3--weak importance; 5--essential importance; 7--very strong importance; and 9--absolute importance.  
[PERSON]'s scale of 1, 3, 5, 7, and 9 was selected to value the importance of criteria/parameters. A lower ticket price, more available space waiting in line, and a shorter time waiting in line were selected as the main parameters to confirm the hypothesis that passengers using LCC services (at the airport terminal facilities) are willing to wait longer and have less space per passenger.  
The first (general information) part (question group I) contains questions where respondents provide answers that largely reflect their opinions, attitudes, and experience as travelers. The analysis of this part of the questionnaire provided a deeper insight to travelers' needs and preferences.  
In the second part (question group II), the AHP method was used, which uses the Saaty scale to assess the relative importance of the defined elements. This scale allows decision-makers to compare elements such as criteria or alternatives in a hierarchy according to their relative importance. The answers to the survey questionnaire, and hence the results of the survey, are presented below.  
Based on the collected data (responses) of the respondents, graphical representations (pie charts and diagrams) were produced via online Google Form tools, as presented in the following Section 4.2.