# Optimizing Flight Delay Predictions with Scorecard Systems
## 4 Research Method
### Database
Figure 1 presents the relative contribution of various delay causes to the total arrival delay time based on U.S. flight data from 2018 to 2022. Departure delays emerge as the dominant factor, accounting for approximately 94% of the total arrival delay minutes. This suggests that delays that occur before take-off are rarely made up during the flight. Late aircraft delays contribute around 41% and carrier-related delays approximately 32%, indicating that previous flight disruptions and airline operational issues are also substantial contributors. In contrast, weather-related delays account for just 6% and security-related issues are negligible (0.1%). The proportions remain relatively stable throughout the year, although a slight decrease in weather-related delays is observed during warmer months, which is consistent with seasonal meteorological patterns. The same analysis was extended to selected groups of origin airports to examine how the causes of delays vary by airport size and traffic volume. Specifically, two subsets were analyzed: the top five origin airports, representing 1,687,276 flights, and the bottom 60 origin airports, comprising 3592 flights. Within the top five airports, the overarching distribution of delay causations exhibits a pattern that closely aligns with the general trend, with a marginal increase in weather-related delays to 8% (Figure 2). These findings imply that although high-traffic airports \begin{table}
\begin{tabular}{c c} \hline \hline
**Variable** & **Description of Variable** \\ \hline CarrierDelay & Carrier Delay in Minutes \\ WeatherDelay & Weather Delay in Minutes \\ NASDelay & National Air System Delay in Minutes \\ SecurityDelay & Security Delay in Minutes \\ LateAircraftDelay & Late Aircraft Delay in Minutes \\ \hline \hline \end{tabular} Source: Authors’ own elaboration.  
\end{table} 
Table 2: Causes of flight delays. In contrast, smaller regional airports (bottom 60) demonstrate less stability in delay shares over months. As shown in Figure 3, these airports experience very high levels of departure delays (up to 98%) with notable contributions from late aircraft delays (33%) and weather-related delays (9%). These fluctuations indicate a higher sensitivity to operational or environmental disruptions, potentially due to limited resources or infrastructure. The delay analyses can be done by scorecard building. This gives us many useful conclusions and interpretations even if the data or the subject of the research is not very well known. Scorecards can be done in an almost automatic way by any analyst or data scientist, and then results can be presented to experts to analyze and interpret them, and finally, to make conclusions for further research. To optimize analyses without losing representativeness and many details, all analyses below were conducted on a sample of 2,055,823 flights randomly generated from all available flights--205,493,100 (flights that were not cancelled, from 1987 to 2023). The modelling uses as a classical approach to verify causal relations between a delayed flight and its cause. The following two statuses are defined in the modelling event:  
* Delayed--a flight with an arrival time delayed by more than 60 min (Level 4). * On-time--a flight with an on time arrival or arrival time delayed less than 60 min (Levels 1-3). The observed share of delayed flights is defined as the delay rate (DR)--this metric reflects the actual, historical proportion of delayed flights in the dataset. The corresponding model-estimated value is the predicted delay rate (PDR), which indicates the probability of delay as forecasted by the scorecard model. These definitions help to distinguish between observed performance and predictive estimation. All data are randomly split into two subsets--training and validation--used, respectively, for model construction and evaluation (see Table 3). Figure 3: Monthly distribution of delay causes of delay as ratio in arrival delay, across the 60 U.S. origin airports with the lowest traffic volume (January–December).