Question: Sofia Airport serves as a base for an Irish low-cost airline founded in what year?
Context: Tiger Airways Australia Pty Ltd, operating as Tigerair Australia, is an Australian low-cost airline.  It commenced services in the Australian domestic airline market on 23 November 2007 as Tiger Airways Australia.  It is a fully owned subsidiary of Virgin Australia Holdings.  The airline is based in Melbourne, Victoria, with its main base at Melbourne Airport.  The Civil Aviation Safety Authority of Australia (CASA) grounded the airline in 2011; as a result operating bases at Adelaide and Avalon were shut down and it initially only operated out of its Melbourne base after returning to the air.  On 7 March 2012, Tigerair announced the reopening of a second base at Sydney Airport. Air Sofia was an airline based in Sofia, Bulgaria.  It operated charter flights to destinations in Europe, Africa, the Far East, South America and the Middle East.  It also leased and wet leased aircraft to other airlines.  Its main base was Sofia Airport. Sofia Airport (IATA: SOF, ICAO: LBSF) (Bulgarian: Летище София, "Letishte Sofiya" ) is the main international airport of Bulgaria located 10 km east from the centre of the capital city Sofia.  In 2015 the airport surpassed 4 million passengers for the first time and handled a total of 4,088,943 passengers, a 7.2% increase compared to 3,815,158 passengers handled in 2014.  In 2016, the number rose to almost 5 million passengers.  The airport serves as the home base for BH Air, Bulgaria Air, and Bulgarian Air Charter and as a base for both Ryanair and Wizz Air.  The Vrazhdebna Air Base of the Bulgarian Air Force is also located at the airport. Serdika Center Sofia is a shopping mall located in Sofia, Bulgaria, opened in the spring of 2010 and has more than 210 stores.  Serdika Center Sofia is located on Sitnyakovo Boulevard, more specifically at the corner of Sitnyakovo Boulevard and Oborishte street, in the municipality of Oborishte.  The shopping mall is only 5 minutes drive from Sofia's main motorway Trakiya, 10 minutes from Sofia Airport and 10 minutes from the central part of Sofia. Ryanair Ltd. (/raɪə'ner/) is an Irish low-cost airline founded in 1984, headquartered in Swords, Dublin, Ireland, with its primary operational bases at Dublin and London Stansted airports.  In 2016, Ryanair was the largest European airline by scheduled passengers flown, and carried more international passengers than any other airline.  (, , NASDAQ: RYAAY ) Norwegian Air Shuttle is a low-cost airline operating from Norway, Sweden, Denmark, Finland, Spain and the United Kingdom.  As of December 2012, it operates to 87 airports in 25 countries across three continents, from its operating bases.  Norwegian was founded in 1993 as a regional airline to operate routes for Braathens SAFE in Western Norway.  It became a domestic, main-haul low-cost carrier from 1 September 2002, when it took into use Boeing 737-300.  In 2006, Norwegian Air Shuttle established its first non-Norwegian base at Warsaw Frédéric Chopin Airport in Poland.  A year later, Norwegian bought the Swedish low-cost carrier FlyNordic, which was merged into Norwegian a year later. Philippines AirAsia, Inc. (formerly Zest Airways, Inc. dba AirAsia Zest), is a low-cost airline based at Ninoy Aquino International Airport in Metro Manila in the Philippines.  The airline is the Philippine affiliate of AirAsia, a low-cost airline based in Malaysia.  The airline started as a joint venture between three Filipino investors and AirAsia Investments Ltd., a subsidiary of AirAsia Berhad. Norwegian Air International is an Irish low-cost airline and a fully integrated subsidiary of Norwegian Air Shuttle, using its corporate identity.  It operates flights to European destinations from several bases in Finland, Spain, Italy and the United Kingdom; and is headquartered at Dublin Airport. Cargoair Ltd, is a Bulgarian cargo airline headquartered in Sofia, Bulgaria.  The company operates charter flights throughout Europe and the Middle East.  The airline's main bases are Leipzig/Halle Airport and Sofia Airport. Hemus Air (Bulgarian title: Хемус Ер) was an airline based in Sofia, Bulgaria.  It operated scheduled domestic and international services from Sofia and Varna, as well as charter, cargo and air ambulance services.  Its main base was Sofia Airport, with a hub at Varna Airport.  After the acquisition of Bulgaria Air, all of Hemus Air's destinations are now under the plate of Bulgaria Air.
Answer: 1984