Oneworld Alliance airlines have California to Baltic nations on sale from $392 to $430 round trip for Sep-Oct departures. Finnair flies SFO-Helsinki nonstop and provides plenty of opportunities to book long overnight transit layovers in Helsinki at these ticket prices. Other itineraries involve AA and BA and as many as 3 stops.
Los Angeles LAX
Santa Ana SNA
San Francisco SFO
San Jose SJC
Riga, Latvia RIX
Tallinn, Estonia TLL
Vilnius, Lithuania VNO
Gdansk GDN and Krakow KRK Poland are other destinations on sale with Oneworld and SkyTeam.
Open-jaw itineraries are possible too, flying to say Riga, Latvia and leaving from Tallinn, Estonia for around $450 round trip.
This is a ticket I would have purchased three weeks ago if available, but I am flying to Prague instead. A similar scene played out this Labor Day weekend to price drops in August with an all alliance fare war to Germany and Central Europe, followed by ticket price drops a couple days later to Baltic cities.
Momondo.com search Omegaflightstore.com ticket
San Francisco SFO – Helsinki HEL (overnight) – Riga, Latvia RIX – Helsinki HEL (overnight) – SFO
SFO – Riga / Tallinn – SFO $452 Open jaw round trip
San Francisco SFO – London LHR – Helsinki HEL – Riga, Latvia RIX / Tallinn TLL – Helsinki HEL (overnight) – SFO
Thu Sep 21 – Thu Sep 28