In the harsh winter, people like to stay indoors in a warm and comfortable environment, watching the snowflakes dance outside the window and enjoying the strong warmth. The same goes for fighter jets. On the cold Scandinavian Peninsula in northern Europe, there are many cave hangars hidden inside the mountains, which are good places for fighter jets to avoid the extreme cold. In the above picture, a Swedish Air Force AJ-37 "Thunder" attack/fighter jet is exiting from a cave hangar, with the vertical tail at the rear of the fuselage folded to one side. The cave in the photo is located in Gothenburg, the second largest city in Sweden, and is now the aviation museum of Gothenburg. In the 1950s, Swedish engineering technicians excavated an underground hangar with an area of 22000 square meters in the rocky mountain here. The size of the hangar is equivalent to four football fields, with the main structure penetrating 30 meters underground. The thick mountain is sufficient to withstand the shock wave of an atomic bomb explosion. After its completion, the hangar was put into operation and maintained military use until 2006. It is reported that 8 fighter jets from the Swedish Air Force's 9th Fighter Squadron are deployed here year-round. These fighter jets complete their preparation in the cave, exit the cave through an upward passage and a low gate, and then taxi to the runway to complete the takeoff operation. The AJ-37 is a multi-purpose fighter developed by the Swedish military enterprise Saab in the 1960s. It can achieve short takeoff and landing in simple conditions such as field airports and road runways, meeting the Swedish Air Force's "air guerrilla warfare" combat concept. The aircraft adopts a unique folding vertical tail, similar to the folding wing design of carrier based aircraft, which allows the aircraft to smoothly pass through low and narrow cave entrances. The AJ-37 fighter jet adheres to the design concept of "one aircraft, multiple types", and has successively developed the AJ-37 attack/fighter jet, SK-37 two seater trainer aircraft, SF-37 tactical reconnaissance aircraft, SH-37 maritime reconnaissance/attack aircraft, etc. The fighter jet in the photo is one of the first AJ-37 fighter/attack aircraft to be put into service, focusing on ground/sea strikes. It can carry Swedish made Rb-04E anti-ship missiles, Rb-05 air to ground missiles, American made AGM-65 "Little Cow" air to ground missiles, as well as rockets, bombs, and aviation mines. It mainly undertakes Swedish territorial air defense operations. (New Society)