There were 4 entrances into underground complex officially called “KLEK”. Main entrance into complex “KLEK” at Airbase Zeljava was entrance No. #2 which was under control of Military Police who where letting in with identity card only. Each of other three entrances was guarded by one soldier. Entrance No. #4 is the most synoptical were armor door are way beyond in the tunnel. Tunnel goes in gentle curve straight to connection with entrance No. #3. Beyond armor door on entrance No. #4, on left side was incavation that was used for storing LORAP films (Long range aerial panoramic photographic system). After that, there was a hydraulic armor door and corridor to “Star” hall and restaurant. On right side was ambulance, 352nd Squadron of recognition classroom.
First corridor leads right from “Star” Hall with washrooms, photo lab and storage for LORAP and guided missile containers and equipment, armourer of 352nd Squadron of recognition and at the end of the corridor were cryptographers. Left corridor was 352nd Squadron of recognition headquarter. In the same corridor was settled intelligence centre, pilot classrooms of 124th and 125th Fighter Aviation Squadrons and parachutist’s room. On the right side of gallery were various containers of jet equipment, air-missile lancers, cannons and firefighting equipment.
From entrance No. #4 until the end of 352nd Squadron of recognition gallery, tunnel is 750 meters long and 12 meters wide. Gallery of 124th Fighter Aviation Squadron was wider where airplanes were stored in Zig-Zag position. At entrance No. #3 was Kerosene storage which might be now instable. Apparently, there were a lot of problems during constructing because of underground gaps and watercourses. During the night you could hear water hum. Inside complex “KLEK” was build in kerosene tank colossal sizes, air condition system, kerosene pipelines and self-power engineering system. All underground complex was alight and air conditioned with constant temperature of 22 degrees of Celsius and humidity because of kerosene evaporation.
Underground facility for high-quality technical maintenance of planes, engines and electronic equipment of aircraft was remarkable construction which was the highest and the widest part of entire complex. It was equipped to support maintenance of 1st, 2nd and 3rd level. Under entire floor of this facility is a huge abyss. Complete Meteorological Service and Flight Control Center were settled in bunker some 60 meters above the underground complex sunken deep into mountain. This bunker was about 70 square meters big and was reached by elevator only. Concrete walls were 2 meters thick build with the best cement and armature. War doctrines were significantly changed during “Cold War” era when Yugoslavian war strategists were thinking about modernization of underground complex which would allow storing of airplanes like MIG-29. However, it was more taken time on precautions for self-destroying of entire underground complex. Five years before the war in Slovenia, enhanced was undermine system.
Underground complex “KLEK” had tunnels and galleries altogether 2.7 kilometers long. It was planned and dimensioned so it can carry between 60 and 80 supersonic jets MIG-21, protecting them from missile and atomic strikes. Alongside, this underground complex was equipped with all necessary supplies to survive conventional and atomic weapons: it had its own airplane technical maintenance room, airplane spare parts and equipment storage, protected and safe storage for rich palette of armament that was carrying MIG-21.
Kerosene has been supplied from Bihac suburbs Pokoj and Orljani where hills have been modified in underground kerosene tanks, especially Grabez hill which was heavily guarded. Kerosene pipeline was 10 kilometers long with pipe diameter of 50 centimeters. Explosive storage was settled in Bihac suburbs Vedro polje, Grabez and Racic, while air bombs were stored in suburb Ripac.
In front of Pljesivica mountain on plateau was built five runways where two of them were dimensioned for landing largest transportation aircrafts. Also, there were three open air parking positions for fighting airplanes that has been 24 hours ready for immediate and urgent take-off which purpose has been to intercept enemy airplanes in air space of Socialist Federal Republic of Yugoslavia. Stone mine that is located on Bosnian side of border dates from airbase construction. Employees parking were near place Baljevac, while “Triangle” runway point was almost 500 meters beyond. Nobody was allowed to park on “Triangle” runway point except jet air-starter trucks. On “Triangle” point road traffic was controlled by signs, road signs and traffic lights.
On Bosnian side near place Baljevac, there was a ramp and entrance processing station that was marked as security point No. #1. 100 meters after this station on left side of road was located security point No. #2. At the same point was located storage of Air Defense Regiment and their weapons: guns 3x20 millimeters, 40 mm L/70 “BOFORS” antiaircraft gun, 9K31 Strela-1 system (NATO reporting name SA-9 “Gaskin”), and radar Giraffe M 85 mounted on domestic FAP 2026 BDS/A truck. Beside guards, from 8 PM until 8 AM, there were two dogs (Riki and Ajax) that were the best “alarms”. After security point No. #2, towards runways and entrances to underground complex, from the right side of road was guardhouse with crew of six guards, military dog handler, deputy commander and guard commander. Guardhouse in the past use to be a primary school before airbase was built. There was another road that was going opposite of underground complex which leads to hunting lodge, beautiful house where one private-housekeeper. This lodge accommodates VIP guests such as Yugoslav Air Force Commander General Anton Tus, Commander General of 5th Air Corps Ljubomir Bajic, and once Chairman of the Presidency of Socialist Federal Republic of Yugoslavia Mr. Dragutin Zelenovic. Guests were usually arriving without previous notice on weekends by Mi-8 helicopter, staying for a night. Some 300 meters away from lodge were handgun range where infantry and officers actively practice. Lodge wasn’t guarded.
At the end of working time, 100 meters from “Triangle” towards place Baljevac was a pick-up point for all officers and other military personals were military buses was parked and driving them homes to Bihac. Each squadron had assigned their bus in case of night flights or working overtime. Drivers of these buses where especially known for managing winter road conditions.