In this study, dynamic panel data analysis focuses on whether the operational conditions that underlie congestion and delays have changed over five summers (when traffic and delays are at their peak) and within the same group of airports, that is, Chicago O'Hare International (ORD), Chicago Midway (MDW), Gary/Chicago International (GYY) and Milwaukee Mitchell International (MKE). Panel data analysis can help to determine whether any change in delays is the result of random or fixed effects. The panel compared the total minutes of gate arrival delay by each summer (time period) and by airport (cross-section variable) as a function of lagged gate arrival delay minutes, arrival demand, arrival volume, taxi-in times and percentage of airport capacity utilised. These variables are usually key factors in congestion and delays. The study reveals that the four airports were mostly subject to fixed effects. This implies that delay reduction initiatives should consider secondary airports in the overall strategy to address congestion and delays at the main hub airports.