Croatia Control (CCL) is a company owned by the Republic of Croatia that provides Air Navigation Services in Croatian airspace. CCL is certified to provide the following services and functions:
- Air Traffic Services (ATS),
- Communication, Navigation, and Surveillance Services (CNS),
- Aeronautical Information Services (AIS),
- Aeronautical Meteorological Services (MET),
- Flight Procedure Design Services (FPD),
- Airspace Management Function (ASM), and
- Air Traffic Flow Management Function (ATFM).
As part of the Air Traffic Services, CCL provides Air Traffic Control Services in Croatian airspace to aircraft whose routes are known in advance through filed flight plans.
In the Republic of Croatia, to ensure the surveillance of controlled airspace for providing Air Traffic Services, all aircraft entering Croatian airspace must use an active detection system (i.e. the so-called transponder). Aircraft that are not equipped with a transponder are not visible in the system used for the provision of Air Traffic Control Services at CCL.
The unmanned aircraft that entered Croatian airspace last night and crashed in the Zagreb area was not equipped with a transponder, and therefore CCL did not detect it with its secondary surveillance radars that are used to monitor aircraft for the purpose of providing CCL’s services.
The subsequent review of data from the Pleso primary surveillance radar, radar reflections and trajectories corresponding to the time and location of the crash of the unmanned aircraft have been detected.