Construction of Airbase Zeljava begins in 1948, searching for micro-location and positioning this huge airport complex. Construction and developing continued until 1968 and that year was considered as ending of construction. Same year, from military airport Pleso near Zagreb (Capital of Croatia) flew whole 117th Fighter Aviation Regiment to Zeljava Airbase near Bihac, Bosnia and Herzegovina.
Concrete building of airbase Zeljava started 1956, but it was in use since 1968 before it was finished because of Soviet invasion on Czechoslovakia. Construction works were continued until 1978. Confidently, it is known that airbase Zeljava was financed by World Bank resources that was previously approved for building motorways in Socialist Federal Republic of Yugoslavia. Construction works were about 4 billion US.
The largest parts of construction were done by Construction Firm “PLANUM” from Belgrade (capital of Serbia and ex-SFRJ) which was than and still is a military construction company. They worked together with their co-operant such as Construction Firm “TEMPO” from Zagreb and Construction Firm “POMGRAM” from Split (Croatia). Military Postal Code for Airbase Zeljava was 4868 which symbolized beginning of the first constructional works (1948) and letting it into function (1968). During constructions, underground complex had official code name “Object 505” and after completion code name was changed into “KLEK”.
After 24 years in fully function and use by Yugoslavian Air Forces, in 1992 this airbase complex were destroyed with 56 tones of explosive which detonations lasts about two days.
Entire airbase occupies space 9 x 4 kilometers, where half of that space belongs to territory of Republic Bosnia and Herzegovina, while other half belongs to Republic Croatia. The nearest city to the airbase Zeljava is Bihac (Bosnia and Herzegovina) where, while airbase was functional, whole airbase crew lived with their families. Configuration of mountain Pljesivica, especially of her highest point (Mt. Gola), gave a good possibility for air-ground defense of underground structure and other ground facilities. During construction of underground structure, first time was applied new system of compartment with core and sprinkle concrete with and without iron net that was later used like carrying armature or as a part of construction, all depending on type and quality of rock mass.
Also, first time was used system catching leakage of water and wet points which were conducted thru drain below underground structure. From all devices that were build in underground structure (officially known as “KLEK”), 95% was made in factories of Socialist Federal Republic of Yugoslavia. With runways on Pljesivica plateau, deep inside mountain Pljesivica was build up a “city” which was protected from atomic impact. For years, mountain Pljesivica was hiding at that time this top secret of Yugoslavian People’s Army and Socialist Federal Republic of Yugoslavia.