Environmental Benefits of Flexible Use of Airspace

Flexible use of airspace (FUA) introduced activation of civil and military airspaces for a defined period rather than being continually designated as purely civil or military. Flight operators that are not users of activated airspaces avoid them with rerouting, which usually results in more miles than planned and has an additional negative effect on the environment. As air traffic recovers to pre-COVID-19 pandemic levels, it is interesting to observe the improvements that FUA has brought with the activation of airspaces for a period shorter than 24 hours. The paper explores the difference in environmental impact with and without FUA. Fast-time simulation is made in Croatian airspace observing three airspaces with different horizontal and vertical limits. Research findings show that FUA decreases the number of aircraft affected by airspace activation compared to 24-hour activation. Decreased number of affected aircraft reduces environmental impact. It can be concluded that the volume of the activated airspace is not as important as its position within the airspace, especially within the terminal airspace. The highest environmental impact is shown, as expected, with an extension of activated airspace to en-route vertical limits, which affected an increased number of flights. Users of FUA should be aware of the environmental impact and air traffic controllers’ workload when deciding upon the period of airspace reservation.