In Chapter ENR 1.9.2 “Airspace Management and the Flexible Use of Airspace in the Republic of Croatia” of the Aeronautical Information Publication (AIP).
The Web AMC Portal is a tool for publishing information on the reservations of airspace structures for end users, but also a tool which will give the registered users an opportunity to make reservations of airspace structures as well as the supporting communication during the process of making a reservation.
ASM is short for Airspace Management; it is a function of planning with the main aim of enabling the maximum utilization of available airspace as a continuous whole, taking into consideration the real short-term needs of different civil and military airspace users (e.g. airline companies, the military, private business aircraft, aero clubs, companies performing aerial work…).
FUA is short for the Flexible Use of Airspace; it is an airspace management concept, according to which airspace should not be determined as completely civil nor completely military, but it should be considered as a whole, to meet the needs of all users to the maximum extent possible.
AMC is short for the Airspace Management Cell, under the existing regulations, responsible for the day-to-day airspace management as a joint civil/military focal point for airspace management in the Republic of Croatia.
Approved Agencies are units authorized by the State to collaborate with the Airspace Management Cell (AMC) regarding the airspace allocation and utilization matters.
The Civil Approved Agency for civil users of airspace structures is the Airspace Utilization Unit of Croatia Control Ltd (CCL), phone: +385 1 6259498, +385 1 6259592, fax: +385 1 6259552, email: firstname.lastname@example.org.
Notice to Airmen (NOTAM) or urgent information is a message sent by telecommunication, which contains information pertaining to the establishment, status or change on any aircraft device or infrastructure, service, procedure or to an air traffic hazard, the timely publishing of which is essential to the flight operations personnel.
UTC stands for the English language term Coordinated Universal Time which is a single international time standard for global aviation, which represents time zero at 0 degrees East/West (the Greenwich Meridian). The expression “summer period” indicates that part of the year in which “daylight saving time” is in force. The other part of the year is named the “winter period”. The “summer period” is introduced every year on the last Sunday in MAR at 0100 UTC and it ceases on the last Sunday in OCT at 0100 UTC. Local time in the Republic of Croatia is UTC+1 hour during the “winter period”, and UTC+2 hours during the “summer period”.
AUP - Airspace Use Plan is an ASM message of the NOTAM status notifying the daily decision of the Airspace Management Cell on the temporary allocation of airspace within its jurisdiction for a specific time, by means of the standard message format.
UUP - Updated Airspace Use Plan is an ASM message of the NOTAM status issued by the AMC to update and supersede an AUP messages/previous UUP information.
AMC must, in the most suitable way for a given airspace situation, restrict or prohibit flights and activities in a specific airspace volume for all users except for the approved users in the following cases:
a. On the request of a state administration body, the Ministry of Defence of the Republic of Croatia, the Ministry of the Interior, the National Protection and Rescue Directorate, if inevitable for the safety of air traffic and other airspace users’ activities, due to the defense needs of the Republic of Croatia, military and police operations, search and rescue operations, fire control, protection of state/government institutions, critical infrastructure and important persons, the protection from the emissions of hazardous and/or harmful substances, gases and phenomena, the Croatian state border control and protection, and the celebration of state anniversaries, parades, and events organized by the state administration bodies.
b. Due to real operational requirements for a period not longer than 48 hours if inevitable for the safety of air traffic and other airspace users’ activities, due to the defense needs of the Republic of Croatia, the military and police operations, search and rescue operations, fire control, protection of state institutions, critical infrastructure and important persons, protection from the emissions of hazardous and/or harmful substances, gases and phenomena, Croatian state border control and protection, and the celebration of state anniversaries, parades, and events organized by the state administration bodies.
On the request of the Airspace Management Cell, and for the purpose of informing all airspace users, the air navigation service provider shall publish all relevant information in a manner common in air traffic.
Having regard to the national interests of the Republic of Croatia and the users’ needs, the following priority list was laid down for the activities which require a reservation of airspace areas:
a. International military exercises and international exercises of other state administration bodies
b. National military exercises and national exercises of other state administration bodies
c. International air shows
d. International championships in aviation activities
e. National championships in aviation activities
f. Military test flights
g. Military and police training
h. Civil training flights
i. Sports and recreational activities of manned aircraft and parachute jumps
j. Sports and recreational activities of unmanned aircraft
k. Airspace activities for which the issuing of a navigational warning for airspace users is required (pursuant to Article 38 of the Ordinance on Rules of the Air)
l. Activities relating to aerial work (aerial spraying, vaccination, crop and infrastructure monitoring, aerial photography...)
m. Releasing and launching objects into the atmosphere (e.g. unmanned free balloons, children’s balloons, sky lanterns, fireworks, lighting effects...)
n. Experimental activities for educational purposes
As an exception to the above mentioned priority rules, the Airspace Management Cell (AMC) can make a decision on the interruption of activities in the reserved airspace in case of the following situations:
a. Flights of the Croatian military aircraft for the purpose of sovereignty protection of the Republic of Croatia (STS/PROTECTED),
b. Search and rescue flights, and humanitarian flights (STS/SAR/HUM),
c. Flights transporting sick or injured persons requiring emergency medical assistance, and the flights for the purpose of providing emergency medical assistance to the sick or injured persons, as well as the flights transporting transplants, blood, and medication, including the flights being conducted to board patients, medication, transplants or blood at the place of aircraft's destination (STS/HOSP),
d. Flights transporting heads of state (STS/HEAD) and flights transporting prime ministers and other state officials with an established preferential status (STS/STATE),
e. Observation flights according to international agreements binding for the Republic of Croatia (Open Skies Treaty),
f. Practice flights of the Croatian military aircraft for interception purposes.
g. For this purpose, all airspace users conducting reservations of airspace structures shall submit to the Airspace Management Cell the contact details of the person responsible/head of activities who shall be available for the Airspace Management Cell via a means of communication (mobile or fixed line) for the whole duration of the activity.
You can find the list of aerodrome operators here.