Question: Which airline that has Chelyabinsk Airport as a secondary hub is based in Yekaterinburg, Russia?

full_context: Document 1: Blue Air: Blue Air is an airline headquartered in Bucharest, with its main hubs at Henri Coandă International Airport and Turin Airport. Since 2016, it has become the largest Romanian airline by scheduled passengers flown. In 2016, Blue Air carried 3.6 million passengers, a significant increase over the 2 million passengers flown the previous year. As of May 2017, Blue Air flies to 70 destinations. Despite operating as a low-cost airline, Blue Air started introducing free sandwiches and drinks on-board shorter flights, and a full hot meal, snacks, hot/cold and alcoholic beverages on longer flights. This is considered unheard of in the low-cost sector, particularly as traditionally 'full service' carriers such as British Airways controversially removed free meals, snacks and drinks in 2017, and is considered key to Blue Air's continued success.
Document 2: Comair (South Africa): Comair Limited is an airline based in South Africa that operates scheduled services on domestic routes as a British Airways franchisee (and an affiliate member of the Oneworld airline alliance). It also operates as a low-cost carrier under its own kulula.com brand. Its main base is OR Tambo International Airport, Johannesburg, and has focus cities at Cape Town International Airport and King Shaka International Airport. Its headquarters are near OR Tambo in the Bonaero Park area of Kempton Park, Ekurhuleni, Gauteng.
Document 3: Ural Airlines: Ural Airlines (Russian: Ура́льские авиали́нии , "Ural’skiye avialinii") is an airline based in Yekaterinburg, Russia, operates scheduled and chartered domestic and international flights out of Koltsovo International Airport. In 2012, the company transported 3.5 million passengers.
Document 4: Enkor: Enkor (full name is "Joint Stock Company (JSC) Enkor") was an airline based in Moscow, Russia. It operated scheduled international passenger services and provided technical aircraft maintenance. Its main bases were Domodedovo International Airport, Moscow, Ulan Ude Airport (UUD) and Chelyabinsk Airport (CEK). In 2004 the airline merged with S7 which inherited their fleet of TU-154M aircraft. The TU-134 and Yakovlev Yak-42 aircraft were retired and the TU-154B2 was sold to Kolavia.
Document 5: Chelyabinsk Air Enterprise: Chelyabinsk Airlines was an airline based in Chelyabinsk, Russia. It operated trunk and regional scheduled and charter passenger flights and also leased aircraft to other operators. It was formerly the Aeroflot Chelyabinsk Division. Its name was often shortened to "Chelal". From 1994 the airline operated Yakovlev 42 tri-jet airliners.
Document 6: Chelyabinsk Shagol Airport: Chelyabinsk Shagol Airport (also Bakal) is an airfield in Russia located in the northwest part of Chelyabinsk. It was the first airport in Chelyabinsk, opened in 1938. Since 1953, all passenger traffic is handled by Chelyabinsk Balandino Airport, and Shagol Airport is used by the local pilots' training school, the Chelyabinsk Red Banner Military Aviation Institute of Navigators. In August 2007 it was used in military exercises of Shanghai Cooperation Organisation. It was a military bomber training base during the Cold War and had about 35 Tupolev Tu-134 UBLs based as recently as 1995. The airport can park over 40 aircraft. It is also used for air shows.
Document 7: MIAT Mongolian Airlines: MIAT Mongolian Airlines (pronounced "me-at", Mongolian: Монголын Иргэний Агаарын Тээвэр , "Mongolyn Irgenii Agaaryn Teever (MIAT)", Mongolian Civil Air Transport) is the Mongolian national airline, headquartered in the MIAT Building in Ulaanbaatar, the capital of Mongolia. The airline operates international scheduled services from its base at Chinggis Khaan International Airport near Ulaanbaatar.
Document 8: Kirensk Airport: Kirensk Airport (Russian: Аэропорт Киренск ) (IATA: KCK, ICAO: UIKK) is an airport in Irkutsk Oblast, Russia located 3 km west of Kirensk. It handles small transport aircraft. This airfield was part of the Yakutsk-Kirensk-Krasnoyarsk leg of the World War II Lend-Lease program Alaska-Siberian (ALSIB) air route.
Document 9: Chelyabinsk: Chelyabinsk (Russian: Челя́бинск ; ] ) is a city and the administrative center of Chelyabinsk Oblast, Russia, located in the northeast of the oblast, 210 km south of Yekaterinburg, just to the east of the Ural Mountains, on the Miass River, on the border of Europe and Asia. Population:  (2010 Census) ;  (2002 Census) ;  (1989 Census)
Document 10: KAPO Avia: KAPO Avia was a large global cargo airline with its main base in Moscow (DME) and a secondary base in Kazan. It operated a fleet of ex-passenger (converted) Ilyushin Il-62M aircraft with a maintenance base capable of maintaining both the Il-62 and the Tupolev Tu-214. KAPO was one of the top ten largest freight carriers in Russia and was owned by the Kazan Aircraft Production Association who manufacture and/or maintain the Tupolev Tu-214, Tupolev Tu-334 and Ilyushin Il-62.
Document 11: United Airlines: United Airlines, Inc., commonly referred to as United, is a major U.S. airline headquartered in Chicago, Illinois. It is the world's third-largest airline when measured by revenue, after American Airlines and Delta Air Lines. United operates a large domestic and international route network, with an extensive presence in the Asia-Pacific region. United is a founding member of Star Alliance, the world's largest airline alliance. Regional service is operated by independent carriers under the brand name United Express. Its main competitors are American Airlines, Delta Air Lines, and Southwest Airlines.
Document 12: Koltsovo Airport: Koltsovo International Airport (Russian: Аэропорт Кольцово ) (IATA: SVX, ICAO: USSS) is the international airport serving Yekaterinburg, Russia, located 16 km (10 mi) southeast of the city. Being the largest airport in Sverdlovsk Oblast, Koltsovo also serves nearby towns such as Aramil, Sysert, and Polevskoy. In general, the airport is responsible for serving approximately 4,290,000 people. The airport is a hub for Ural Airlines, RusLine and Aviacon Zitotrans. Due to its location in the center of Russia, Yekaterinburg's airport is included in the "Priority Airports" list of Russia's Federal Air Transport Agency (Rosaviatsia).
Document 13: Turkish Airlines: Turkish Airlines (Turkish: "Türk Hava Yolları") () is the national flag carrier airline of Turkey, headquartered at the Turkish Airlines General Management Building on the grounds of Atatürk Airport in Yeşilköy, Bakırköy, Istanbul. s of 2017 , it operates scheduled services to 302 destinations in Europe, Asia, Africa, and the Americas, making it the fourth-largest carrier in the world by number of destinations. It serves more destinations non-stop from a single airport than any other airline in Europe. Turkish Airlines flies to 120 countries, more than any other airline. With an operational fleet of fourteen cargo aircraft, the airline's cargo division serves 64 destinations. Istanbul Atatürk Airport is its main base, and there are secondary hubs at Esenboğa International Airport, Sabiha Gökçen International Airport, and Adnan Menderes Airport. Turkish Airlines has been a member of the Star Alliance network since 1 April 2008.
Document 14: Chelyabinsk Airport: Chelyabinsk Airport (IATA: CEK, ICAO: USCC) is an airport in Russia located 18 km north of Chelyabinsk. It services large airliners and can park up to 51 aircraft. It also serves as a secondary hub for S7 Airlines and Ural Airlines.
Document 15: Urumqi Air: Urumqi Air () is an airline headquartered in Ürümqi, Xinjiang, People's Republic of China. It operates scheduled passenger services. Its main hub is Ürümqi Diwopu International Airport in Ürümqi. The airline is one of the four the founding members of the U-FLY Alliance.
ground_truth: Ural Airlines