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 airbase - 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, India, Pakistan, Italy, North Korea, Norway, Sweden, Switzerland, Taiwan, Vietnam and Yugoslavia.

India
The Indian Air Force operates underground hangars. Sukhoi Su-30 MKI have been stationed at Trishul Air-base situated in Bareilly, Uttar Pradesh, India. It houses one of the largest underground hangars in Asia. Adampur, situated in Punjab, houses an air-base with underground hangars. It is the home base for MiG-29 and MiG-21 interceptors.

Pakistan
Pakistan has an underground hangar facility for the Pakistan Air Force at PAF Base Mushaf, Sargodha, Punjab.

Sweden
The Swedish Air Force has used underground hangars. The Saab 37 Viggen aircraft was designed with a folding tail fin to fit into low hangars. One of the hangars is now the Aeroseum museum.

Switzerland
Six Flugzeugkaverne (aircraft caverns), each with space for 30 or more aircraft, were constructed for the Swiss Air Force. One has been used to operate F/A-18 Hornet aircraft.

Yugoslavia
The largest underground hangar complex in former Yugoslavia was at Željava Airport near Bihać, with enough space for 80 MiG-21s. Slatina Air Base, located at Pristina International Airport, contained the second largest.

Taiwan
The only Taiwanese airbase where has built underground hangars is Jiashan Airbase, located in Hualien at Eastern Taiwan coast, to prevent from massive missile strike launched from China. Underground hangars in Jiashan Airbase has deployed F-16 A/B, F-5 E-F squadrons.

Saudi Arabia
During the Gulf War, USAF and Saudi Air Force utilized underground hangars with good desert camouflage, and launched air raids against Saddam Hussein's air powers.