# Underground hangar

An underground hangar is a type of hangar for military aircraft, usually dug into the side of a mountain for protection. It is bigger and more protected than a hardened aircraft shelter (HAS).
An underground hangar complex may include tunnels containing the normal elements of a military air base—fuel storage, weapon storage, rooms for maintaining the aircraft systems, a communications centre, briefing rooms, kitchen, dining rooms, sleeping areas and generators for electrical power.
Countries that have used underground hangars include Albania, China, Italy, North Korea, Norway, Sweden, Switzerland, Taiwan, Yugoslavia, Iran, Vietnam, South Africa and Pakistan.

## By country
### Albania

Underground hangar at Kuçovë Aerodrome near Perondi.
Underground hangar at Gjadër Aerodrome.

### Iran

In 2023, Iran unveiled a large underground base called "Eagle 44": in this base, Iran's upgraded F-4 Phantom fighters were present under Shahid Doran. Also, pictures and replicas of Su 35 were seen in that base. This base, where Iranian drones are also present, is probably somewhere in the south of Iran. While broadcasting a video of another base, on the other side of which Su-24 Fencer aircraft equipped with +2000 km cruises, Iran announced that it has more underground bases that will be unveiled in the future.

### Israel

Eight Israeli air force F-16I Sufa fighter aircraft were damaged in the winter of early 2020 by flooding when they were improperly left inside underground hangars in a Negev desert airbase during severe flooding. The Washington Post reported in 2012 based on the results FOIA requests to the US government that the US Army Corps of Engineers brought in US construction contractors to build installations in the south of Israel including underground hangars for fighter-bombers as a part of US military aid to Israel.

### Italy

Built in World War II on the Island of Pantelleria at Pantelleria Airport.

### North Korea

There are at least twenty major airfields with underground hangars in North Korea, including Onchon air base, Kang Da Ri Airport and Sunchon Airport.

### Norway

Underground hangars were built in Bodø Main Air Station and Bardufoss Air Station.

### Sweden

In 1941 the Swedish Air Force began building its first underground hangar at Göta Wing (F 9), located near Gothenburg in south-west Sweden, it was commissioned in 1944. After World War II plans were made up for building underground hangars at every air force base that had suitable rock conditions. These ambitious building plans proved to be too expensive and were reduced to hangars at certain select air bases. A second underground hangar was built in 1947 at Södertörn Wing (F 18). After that plans were finalized for building underground hangars capable of surviving close hits by tactical nuclear weapons. This required that these new hangars be much deeper, with 25 to 30 meters of rock cover, and heavy-duty blast doors in concrete. The Saab 37 Viggen aircraft was designed with a folding tail fin to fit into low hangars. Aeroseum, an aircraft museum open to the public in Gothenborg, is housed in the larger cold war era Underground Hangar at Säve.

### Switzerland

Six Flugzeugkaverne (aircraft caverns), each with space for 30 or more aircraft, were constructed for the Swiss Air Force. One at Meiringen Air Base has been expanded to operate F/A-18 Hornet aircraft. Originally, the plan for the aircraft hangar (German Kavernenflugplatz) included the possibility of launching combat aircraft from the mountain air base. High costs and technical difficulties prevented these plans from being realised. The idea of using roads as runways was later part of the design demands for the Swiss motorway network.

### Taiwan

Chiashan Air Force Base, located in Hualien, has an extensive underground hangar system which can accommodate two hundred aircraft.
Chihhang Air Base in Taitung County can accommodate eighty aircraft in underground hangars.

### Former Yugoslavia

The "Objekat" series of military installations can be found in secluded but strategically important areas within the former Yugoslavia, and the construction of these military bases were initialized by the SFRJ's defence ministry.
During the Yugoslav Wars, most of these bases were used by the Serbs in certain operations, but due to circumstances imposed by the Croat forces, they were destroyed and later rendered useless for military use. Nowadays, they are popular for urban exploration, however it is risky due to the chances of anti-personnel landmines being located in unexplored areas.
Object 505 "Klek" at Željava Airport near Bihać. Built in 1958-1968. The largest underground hangar complex in former Yugoslavia, with enough space for 80 MiG-21s. There was intercept and surveillance radar "Celopek" at nearby mountain Gola Plješevica (1648 m).
Object "Morava" at Slatina Air Base, located at Pristina International Airport. The second largest underground hangar complex in Yugoslavia.
Object "Buna" at Mostar International Airport. Built in 1969-1971.
Object "Cetina" at Split Airport near Split. Built in 1969-1970.
Object "Šipčanik" at Podgorica Airbase near Podgorica (1946-1992 Titograd). Today wine cellar.