Sign a comprehensive agreement. However: passengers may have to accept two transfers.
The Latvian airline Air Baltic stays away from aviation alliances, but cooperates with numerous airlines within the framework of codeshare and interline agreements. You haven't been flying long-haul yourself for a long time, but you offer various destinations in cooperation with partners. This is now being deepened, as a comprehensive codeshare contract has been concluded with Icelandair.
This is a win-win situation for the two carriers, because Air Baltic has access to further long-haul destinations via Keflavik and, conversely, Icelandair can offer further destinations in Eastern Europe and the Baltic countries. However, there is one catch for the passengers: under certain circumstances, two transfers (in Riga and Keflavik) may be necessary.