United is challenging Norwegian Airlines in its San Francisco Bay Area market with fares under $600 for San Francisco to Stockholm round trip. These fares are available until June 1 and again from August 10.
This fare has many routes through Europe with Star Alliance carriers for travel on Swiss to Zurich, Lufthansa to Munich and Frankfurt or SAS to Stockholm for $30 to $50 more per ticket.
The window for low rates is June 1 latest departure before peak season summer fares and August 10 is when low fares resume. United has $595 fares for some dates before June 1 and after August 10.
Monday August 10 to Wednesday, August 19, 2015
$654 is flight booked with United or $674 with Lufthansa.
Lufthansa Flight #455 A380 SFO-FRA, 2:55pm – 10:50am
This itinerary has a 9 hour layover in Frankfurt. Other dates and schedules can reduce the layover to under 2 hours.
SAS Flight #674 Boeing737 FRA-ARN Stockholm 7:50pm – 9:55pm.
A 9-hour layover in Frankfurt might be highly undesirable for some travelers. I like finding flights with layovers long enough to sightsee for a few hours in another city where I transit on the way to the destination.
June 1 is the latest date I see the low fare of $654 with a return date June 10 or $684 to return June 17 or $719 to return June 24 if you want the grand tour length of stay.
After June 1 airfare rates rise to over $1,000 round trip.
Rates are rising as I type this with some fares rising to $611. Check out the deals. They will likely be gone by end of day.
http://www.theflightdeal.com/ is a good website to check for daily low fares. There is another great fare under $600 from SFO to Sao Paulo on Aeromexico today and $647 LAX-Billund, Denmark on British Airways.