Oneworld Alliance airlines have San Francisco to Vienna, Austria priced around $400 round trip as American Airlines tickets for travel January to March, then $377-$384 for April travel. Lowest fares are departures Sunday to Tuesday outbound.
Many of the itineraries fly Finnair via Helsinki in one or both directions.
American Airlines tickets for Finnair flights
San Francisco SFO – Helsinki HEL – Vienna VIE – Helsinki HEL – SFO