Flights London → San Francisco — September 21, 2026

One way · Economy · 1 adult · price per person

The cheapest itinerary observed for Monday, September 21, 2026 on the London–San Francisco route: 2 stops itinerary (3 flights) via Madrid (MAD) and Lisbon (LIS), from London Stansted (STN) to San Francisco International (SFO), first flight Ryanair UK RK2628, departs 5:55 AM, arrives 1:35 PM the next day, total travel time 39h 40m including layovers, flight time 16h 20m (layovers excluded), $555 per person. Fare as listed by Aviasales: carry-on bag not included (personal item only), checked bag not included, changes not allowed, non-refundable. Price found in an Aviasales search on September 9, 2026 and read by AirSource on September 10, 2026, 19:03 UTC: it is not guaranteed and is confirmed on Aviasales at booking time. The cheapest direct flight observed: United Airlines UA949, from London Heathrow (LHR) to San Francisco International (SFO), departs 1:00 PM, arrives 4:05 PM, direct, 11h 5m, $639 per person. Fare as listed by Aviasales: carry-on bag not included (personal item only), checked bag not included, changes not allowed, non-refundable.