British Airways and American Airlines have San Francisco and San Jose to Barcelona on sale from $455 to $521 round trip for departures from August to October.
British Airways AARP discount rates drop the ticket prices to $455.
The airline websites are pricing from $477 to $521.
British Airways San Jose SJC – London LHR – Barcelona BCN – London LHR – San Jose SJC
Momondo.com search for British Airways ticket with long overnight layover in London both ways.
British Airways San Jose SJC – London LHR (20h 30m layover 2:20pm-10:50am) – Barcelona BCN – London LHR (22h 30m layover 4:25pm-2:55pm) – San Jose SJC