Air Canada frequently has the lowest prices for round trip travel to Europe from San Francisco. Copenhagen is on sale for as low as $313 through Momondo.com online travel agency sites and $384 through United.com for travel departures in February and March 2018. Ticket prices are about $50 to $80 more for April-May travel.
I flew Air Canada from Copenhagen to San Francisco this week and it was a comfortable flight in economy class with a decent IFE system, although my headphone jack was screwed up and I had a hand cramp from holding my earbuds pin in place for 8 hours of films. And the rewind did not work on my IFE, if I happened to miss any portions of film sound. My wife’s IFE worked normally.
TicketMerry.com (Momondo.com search)
Air Canada operated flights, marketed as United flights
SFO – Toronto YYZ – Copenhagen CPH – YYZ – SFO
The main issue we had with our flight in Toronto going through US passport control at YYZ was the entire 2 hours of transit time was used up waiting in line and we barely made our flight to SFO.
It all worked out and we got home as planned.