The operation of global air transportation system is based on the safety and efficiency of provided services. Limiting airspace by closing some volumes requires reconfiguration of airplane trajectories. Russian-Ukrainian war led to the closure of the Ukrainian airspace for any civilian use since February 24, 2022. Airspaces of the Russian Federation and Belarus are limited in use due to sanctions and the high risk of military actions. In addition, ongoing military conflicts in the Middle East region hold airspaces of Afghanistan, Iran, Iraq, Syria, and Yemen at high risk for civil aviation. Airspace users have to avoid entering closed airspace, which results in increased trajectory length, total flight time, aircraft costs, and ticket prices for passengers. In our study, we analyzed the configuration of the closed airspace and its impact on the global air transportation system. A global air transportation graph is used to estimate additional trajectory length and horizontal flight efficiency for a particular departure airport. The impact of closed airspace configuration is estimated based on cumulated functions of the affected area by particular levels of additional trajectory length and horizontal flight efficiency index. Affected areas are estimated for Schiphol (EHAM) and O'Hare (KORD) international airports. Statistical analysis of trajectory data of particular flights indicates a significant increase in additional trajectory length and total flight time. The proposed model has been verified by comparison with the results of trajectory data analysis of 20 unique flight connections.