Dubbed “Eagle 44,” the base is reportedly capable of handling a variety of aircraft, both manned and unmanned, including fighter jets and strike aircraft. The Iranian Air Force doesn’t have any large strategic bombers, but uses a number of ground attack jets including the Su-24, Su-22, Mirage F1, and F-4 Phantom.
The facility is also equipped with alert and command posts, aircraft hangars, maintenance facilities, navigational facilities, and fuel tanks to support air operations.
Footage from Iranian media showed the air base in action, with American-made F-4s rolling through the concrete facility. It is clearly made to withstand American “bunker-buster” bombs designed to penetrate ordinary reinforced structures and those just beneath the surface.
"It is one of the army's most important air force bases, with fighters equipped with long-range cruise missiles and built in the depths of earth,” Iranian news said.
However, the video makes clear that while the air base’s facilities are all underground, the runway itself is not, and aircraft must pass through a narrow gateway to access the facilities. That gateway is protected by thick blast doors.
According to Iranian media, Eagle 44 isn’t the Iranian military’s first underground air base.
Tehran has long used the country’s many mountain ranges to conceal military facilities from observation and attack, dating back to the Iran-Iraq War of the 1980s. These have included so-called “missile cities” that are purported to be connected to a network of underground missile silos. The Islamic Revolutionary Guard Corps has even buried ballistic missiles in the ground to hide them.
Other countries use underground bases, too, including Sweden and China, both of which have naval bases cut into mountains from the sea. Switzerland, mountainous and defense-minded like Iran, has also concealed air bases underground in mountainsides.