Who/What is Oneworld Member "S7"?

From Wikipedia:

OJSC Siberia Airlines (Russian: ОАО «Авиакомпания „Сибирь“» "ОАО Aviakompania Sibir"), operating as S7 Airlines, is an airline headquartered in Novosibirsk Oblast, Russia,[sup][1][/sup][sup][2][/sup] with offices in Moscow.[sup][3][/sup] S7 Airlines has been Russia's fastest-growing airline and recently passed Aeroflot as Russia's largest domestic airline.[sup][4][/sup]
S7 has operated scheduled passenger flights to destinations in Russia, as well as international services to Armenia, Austria, Azerbaijan, Bulgaria, PR China, Czech Republic, Egypt, Georgia, Germany, Hong Kong, Ireland, Kazakhstan, Kyrgyzstan, Moldova, Montenegro, Korea (South), Spain, Tajikistan, Thailand, Turkey, Turkmenistan, Uzbekistan, Ukraine and the United Arab Emirates. Its main bases and hubs have included Moscow Domodedovo International Airport (DME) and Novosibirsk Tolmachevo Airport (OVB), with a further hub at Irkutsk Airport (IKT), Irkutsk. After 2004, it became the largest domestic route airline network in Russia.
 
From the website

S7 Airlines

The airline has the widest domestic route network in Russia, created on the basis of two air transport hubs at Moscow (Domodedovo) and Novosibirsk (Tolmachevo). It also has regular flights to the countries of the CIS, Europe, the Near East, South-East Asia and to countries in the Asia-Pacific region.
The airline’s story began in 1957, with the first civil flight from a military airport in Novosibirsk, by the Tolmachevo united air group; Sibir Airlines was based on that group. Since 2005 Sibir Airlines has operated under the brand S7 Airlines.
 
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