WestJet and Norwegian Airlines both have one way deals from San Francisco to London Gatwick on several dates in July and early August. WestJet is $239 one way with an opportunity on some dates for a near 24 hour layover in Vancouver, British Columbia.
Norwegian will fly you nonstop SFO to London for $270 on some dates.
Ticket prices are $500 to $600 one way from London back to SFO, so this deal is for people who have miles to fly back to California on an award ticket or can stay in Europe long enough until lower ticket prices return beginning in early to mid-August. There are also ticket opportunities to fly from London, Spain and Scandinavian cities in July and August for $600 to $700 round trip with a return flight to Europe months later.
Loyalty Traveler – My Europe under $600 round trip ticketing strategy for summer and Christmas (April 24, 2019).
Norwegian Airlines also has $140 one way flights for travel October to December.
Norwegian is one of my favorite airlines. Typically I watch four movies during the 10 hour flight and practice listening to my Norwegian or Swedish through English-subtitled Scandinavian films. I generally book a basic ticket with no checked bag or prepaid seat. More often than not I end up with a window or aisle seat for free and bring a free carry-on bag for the overhead bin and place my backpack under the seat. Empty seats or empty cabin bin space usually means I put my backpack elsewhere during the flight.
WestJet is an airline I have never flown.
Norwegian Airlines San Francisco SFO – London Gatwick LGW
WestJet Airlines appears to have same cabin bag rules as Norwegian with one carry-on bag allowed for overhead bin and one personal underseat bag. Checked bag fee is $30 USD, less than $45 Norwegian checked bag fee.
Monday July 15 San Francisco SFO – Vancouver YVR (22 hour layover arrive YVR 6:08pm)
Tuesday July 16 Vancouver YVR – London Gatwick LGW (depart 4:18pm)