The cheapest London Stansted to San Francisco return flight on the radar right now is £844, flying with Turkish Airlines via one or more connections. It covers departures in January 2027, and every dated link below opens that exact STN–SFO search on Skyscanner. The price we usually record on this route is £756. Across 105 recorded checks it has ranged between £425 and £1,522. Our sampling points to January 2027 as the cheapest month to fly London Stansted to San Francisco.
Prices are re-checked against Skyscanner automatically, and every one shows when it was last confirmed, so nothing here is older than it looks. Not flying from London Stansted? We track 60 other departure cities for San Francisco, listed at the foot of this page.
Prices like this tend to vanish fast. If it has gone when you look, try the days either side of the dates above, since London Stansted to San Francisco is often still worth booking within a day or two of the fare we found.