Question: When did Swedish become the official language of the country the founders of Air Greenland are from?

full_context: Document 1: Airport: Most of the world's airports are owned by local, regional, or national government bodies who then lease the airport to private corporations who oversee the airport's operation. For example, in the United Kingdom the state-owned British Airports Authority originally operated eight of the nation's major commercial airports - it was subsequently privatized in the late 1980s, and following its takeover by the Spanish Ferrovial consortium in 2006, has been further divested and downsized to operating just five. Germany's Frankfurt Airport is managed by the quasi-private firm Fraport. While in India GMR Group operates, through joint ventures, Indira Gandhi International Airport and Rajiv Gandhi International Airport. Bengaluru International Airport and Chhatrapati Shivaji International Airport are controlled by GVK Group. The rest of India's airports are managed by the Airports Authority of India.
Document 2: Languages of Sweden: Swedish evolved from Old Norse around the 14th and 15th century, and historically, the Swedish dialects were generally much more different than today. Since the 20th century Standard Swedish prevails throughout the country. The Scandinavian languages constitute a dialectal continuum and some of the traditional Swedish dialects could equally be described as Danish (Scanian) or Norwegian (Jamtlandic).
Document 3: Korean Air: Korean Air's international passenger division and related subsidiary cargo division together serve 127 cities in 44 countries, while its domestic division serves 12 destinations. It is among the top 20 airlines in the world in terms of passengers carried and is also the top-ranked international cargo airline. Incheon International Airport serves as Korean Air's international hub. Korean Air also maintains a satellite headquarters campus at Incheon. The majority of Korean Air's pilots, ground staff, and flight attendants are based in Seoul.
Document 4: Sabena: The Societé Anonyme Belge d'Exploitation de la Navigation Aérienne (French; "Belgian Corporation for Air Navigation Services"), better known internationally by the acronym Sabena or SABENA, was the national airline of Belgium from 1923 to 2001, with its base at Brussels National Airport. After its bankruptcy in 2001, the newly formed SN Brussels Airlines took over part of Sabena's assets in February 2002, which became Brussels Airlines after a merger with Virgin Express in March 2007. The airline's corporate headquarters were located in the Sabena House on the grounds of Brussels Airport in Zaventem.
Document 5: Qantas: Qantas flies to 20 domestic destinations and 21 international destinations in 14 countries across Africa, the Americas, Asia, Europe and Oceania excluding the destinations served by its subsidiaries. The entire Qantas group serves 65 domestic and 31 international destinations.
Document 6: United Nations Regional Groups: the African Group, with 54 member states the Asia - Pacific Group, with 53 member states the Eastern European Group, with 23 member states the Latin American and Caribbean Group (GRULAC), with 33 member states the Western European and Others Group (WEOG), with 28 member states, plus 1 member state (the United States) as an observer state.
Document 7: Dutch language: Old Dutch naturally evolved into Middle Dutch. The year 1150 is often cited as the time of the discontinuity, but it actually marks a time of profuse Dutch writing and during this period a rich Medieval Dutch literature developed. There was at that time no overarching standard language; Middle Dutch is rather a collective name for a number of closely related dialects whose ancestor was Old Dutch. But they were all mutually intelligible. In fact, since Dutch is a rather conservative language, the various literary works of that time today are often very readable for modern-day speakers.
Document 8: Sterling Airlines: Sterling Airlines A/S was a low-cost airline with its head office at Copenhagen Airport South in Dragør, Dragør Municipality, Denmark. It was created in September 2005 through the merger of two Danish airlines — Sterling European Airlines and Maersk Air — which had been acquired by the Icelandic investment group Fons Eignarhaldsfélag a few months before for MDKK 500. Fons was owned by Icelandic business tycoon Palmi Haraldsson. One month after the merger, Sterling Airlines was sold to the FL Group for an amount of MDKK 1500. In December 2006, Sterling was sold again, this time to Nordic Travel Holding. On 6 January 2006, Hannes Þór Smárason, CEO of the FL Group, stated that a merger of EasyJet and Sterling was a possibility.
Document 9: List of SAS Group destinations: SAS Group destinations This is a complete list of the SAS Group airlines destinations, including Air Greenland, Scandinavian Airlines and Widerøe. In September 2010 the SAS Group airlines served 180 destinations in 35 countries on 4 continents.
Document 10: Avianca Costa Rica: Avianca Costa Rica, formerly known as "LACSA" ("Spanish: Lineas Aéreas Costarricenses S.A."), minority owned by the Synergy Group, is the national airline of Costa Rica and is based in San José. It operates international scheduled services to over 35 destinations in Central, North and South America. The airline previously used the TACA/LACSA moniker when it was a subsidiary of Grupo TACA. Since May 2013, following Avianca's purchase of Grupo TACA, Avianca Costa Rica became one of seven nationally branded airlines (Avianca Ecuador, Avianca Honduras, etc.) operated by Avianca Holdings group of Latin American airlines.
Document 11: Switzerland: Aside from the official forms of their respective languages, the four linguistic regions of Switzerland also have their local dialectal forms. The role played by dialects in each linguistic region varies dramatically: in the German-speaking regions, Swiss German dialects have become ever more prevalent since the second half of the 20th century, especially in the media, such as radio and television, and are used as an everyday language, while the Swiss variety of Standard German is almost always used instead of dialect for written communication (c.f. diglossic usage of a language). Conversely, in the French-speaking regions the local dialects have almost disappeared (only 6.3% of the population of Valais, 3.9% of Fribourg, and 3.1% of Jura still spoke dialects at the end of the 20th century), while in the Italian-speaking regions dialects are mostly limited to family settings and casual conversation.
Document 12: Air Greenland: Air Greenland A/S, also known as Greenlandair, is the flag carrier airline of Greenland, jointly owned by the SAS Group (37.5%), the Greenlandic Government and the Danish Government. It operates a fleet of 32 aircraft, including 1 airliner used for transatlantic and charter flights, 9 fixed-wing aircraft primarily serving the domestic network, and 22 helicopters feeding passengers from the smaller communities into the domestic airport network. Flights to heliports in the remote settlements are operated on contract with the government of Greenland.
Document 13: SAS Group: SAS AB (Scandinavian Airlines System Aktiebolag) (, , ), trading as SAS Group, is an airline holding company headquartered in the SAS Frösundavik Office Building in Solna Municipality, Sweden. It is the owner of the airlines Scandinavian Airlines and Scandinavian Airlines Ireland. SAS once owned 19.9% of the now defunct Spanish airline Spanair as well as shares in Estonian Air and Skyways Express. It also owns the aviation services companies SAS Business Opportunities, SAS Cargo Group, SAS Ground Services and SAS Technical Services. In addition, it holds minority ownership of Air Greenland. SAS Group is partially owned by the governments of Sweden and Denmark with a 21.4% and 14.3% ownership, respectively. The remaining 64.3% is held by private owners, of which Foundation Asset Management owns 7.6%. The company is listed on the Oslo Stock Exchange, the Stockholm Stock Exchange, and the Copenhagen Stock Exchange.
Document 14: Old English: Old English developed from a set of Anglo-Frisian or North Sea Germanic dialects originally spoken by Germanic tribes traditionally known as the Angles, Saxons, and Jutes. As the Anglo-Saxons became dominant in England, their language replaced the languages of Roman Britain: Common Brittonic, a Celtic language, and Latin, brought to Britain by Roman invasion. Old English had four main dialects, associated with particular Anglo-Saxon kingdoms: Mercian, Northumbrian, Kentish and West Saxon. It was West Saxon that formed the basis for the literary standard of the later Old English period, although the dominant forms of Middle and Modern English would develop mainly from Mercian. The speech of eastern and northern parts of England was subject to strong Old Norse influence due to Scandinavian rule and settlement beginning in the 9th century.
Document 15: Old English: Old English is a West Germanic language, developing out of Ingvaeonic (also known as North Sea Germanic) dialects from the 5th century. It came to be spoken over most of the territory of the Anglo-Saxon kingdoms which became the Kingdom of England. This included most of present-day England, as well as part of what is now southeastern Scotland, which for several centuries belonged to the Anglo-Saxon kingdom of Northumbria. Other parts of the island – Wales and most of Scotland – continued to use Celtic languages, except in the areas of Scandinavian settlements where Old Norse was spoken. Celtic speech also remained established in certain parts of England: Medieval Cornish was spoken all over Cornwall and in adjacent parts of Devon, while Cumbric survived perhaps to the 12th century in parts of Cumbria, and Welsh may have been spoken on the English side of the Anglo-Welsh border. Norse was also widely spoken in the parts of England which fell under Danish law.
ground_truth: 20th century
sub_queries: Air Greenland >> founded by Answer: Scandinavian Airlines
Scandinavian Airlines >> country Answer: Sweden
when did swedish become the official language of Sweden Answer: 20th century