## 2 Theoretical Background
In 1992, [PERSON] and [PERSON] [8] were two of the first researchers to raise methodological questions in the passenger terminal design. Later models were improved with technological development and are constantly adapted to passengers. However, even though there are various models aiming at passenger flow improvement [21], there is still no unified model for the optimization of the entire airport passenger terminal system, and various researchers use different optimization approaches. Consequently, there is an evident need for additional optimization of airport terminal facilities, in relation to airline business models, in order to maximize the capacity and operational efficiency of the passenger terminal. An overview of relevant studies with highlighted contributions is provided in the following Table 1. \begin{table}
\begin{tabular}{c c c c} \hline
**Research** & **Methodology** & **Contribution** & **Airports** \\ \hline \multirow{3}{*}{[PERSON] et al., 2001 [22]} & Analytical & \multirow{3}{*}{Analysis and capacity assessment of airport terminal facilities} & Milan Airport \\  & method—AIRLAB & & \\ \hline \multirow{3}{*}{[PERSON] and 2001 [23]} & \multirow{3}{*}{Simulation method—AIRLAB} & Creation of a flexible model for & \\  & & defining and applying & \\ \cline{1-1}  & & alternative operational policies & \\ \cline{1-1}  & & in the terminal; modeling of & Milan Airport \\ \cline{1-1}  & & passenger behavior; animation & \\ \cline{1-1}  & & of operations inside the terminal & \\ \hline \multirow{3}{*}{[PERSON] and [PERSON], 2003 [24]} & Simulation method—ARENA & Traffic flow optimization and & Kansai International \\ \cline{1-1}  & & queue reduction & Airport \\ \hline \end{tabular}
\end{table} 
Table 1: The methodologies used in the optimization of the passenger terminal—literature overview. \begin{table}
\begin{tabular}{c c c c} \hline
**Research** & **Methodology** & **Contribution** & **Airports** \\ \hline [PERSON] et al., 2003 [25] & Linear programming method & Reduced total working hours of check-in; improved passenger terminal performance & Ottawa International Airport \\ \hline  & & & Birmingham Airport, \\  & & & Brisbane Airport, Hong \\  & & & Kong International \\  & & system costs & Airport, Melbourne \\  & & & Airport, Orlando \\  & & & International Airport \\ \hline  & & & \\  & & & \\  & Simulation & & \\  & method—ARENA & Optimized check-in counters and security control units; & \\  & & & \\  & & & \\  &  
Considering the relevant literature, this paper proposes a methodology for planning (optimizing) the capacity of airport terminal facilities at passenger terminals where there is a visible trend of change in the share of airline business models from FSC to LCC, based on forecasts of traffic demand and the shares of airline business models. As per the review of the previous literature (Table 1), it can be concluded that there is no similar methodology used, which combines forecasts of traffic demand and the share of airline business models as a basis for proposing modifications to airport infrastructure, specifically the passenger terminal. Thus, this paper contributes with new insight/approach in the field of airport planning, as well as in optimizing passenger terminal capacity with regard to future changes in the air transport business environment. In accordance with the obtained estimates of traffic demand and the share of airline business models, it is possible to plan in detail the airport terminal facilities, in this case Pula Airport, which allows for airport terminal capacity optimization and improvement of the level of service.