Amazing to see San Francisco to London LHR at $437 round trip flying Virgin Atlantic nonstop in late July with one-stop Delta flights in early August for the return. SkyTeam ticket prices drop to $415 round trip from August to March.
United Airlines has one-stop flights SFO-LHR beginning August 11 for as low as $420 round trip. Nonstop flights from $428 are available from August 18. Low United/Star Alliance fares are available through March 2020.
Delta Airlines San Francisco SFO – London LHR (Virgin Atlantic) – Detroit DTW – San Francisco SFO (Delta)
$437.23 round trip Monday July 29 – Thursday August 8
United Airlines San Francisco SFO – London LHR – San Francisco nonstop flights
$427.13 round trip Sunday August 18 – Wednesday August 28