Oneworld members Finnair and S7 Airlines have agreed a handful of new codeshares to start in April.
Finnair's AY code will from April 26 be added to S7's new service between Helsinki and Moscow's Domodedovo International Airport.
Also from that date, AY will be added to selected onward S7 services from Domodedovo to Novosibirsk, Kazan, Rostov-on-Don, Samara, Ufa and Yekaterinburg.
In return, S7 will add its flight code to selected Finnair services from St Petersburg and Yekaturinburg to Helsinki, and to selected onward Finnair services to the Finnish cities of Joensuu, Kuopio, Oulu, Rovaniemi, Tampere, Turku and Vaasa.
Hannu Sundberg, Finnair's vice-president of commercial partnerships, said: "We are looking forward to welcoming S7 Airlines to Helsinki with their new service from Domodedovo.
"The arrival of another modern, high-quality alliance partner in Helsinki also reinforces a vital oneworld hub between east and west."
Vadim Besperstov, S7 Airline's director of strategy department, added: "On April 26, S7 Airlines starts its own flights to Helsinki from Moscow's Domodedovo airport. As a result of this agreement, passengers of S7 Airlines and Finnair will be able to travel inside both countries to more destinations."
Last week, Finnair announced that it is adding an extra three weekly services onto its Bangkok route next winter (see news, February 28).