American Airlines offers summer travel deals Switzerland with San Francisco to Zurich ZRH at $490 in July and Basel BSL for $539 round trip. Even lower ticket prices are available for August 2018 travel with Zurich $436 and Basel $458 round trip.
American Airlines $489.51 round trip
San Francisco SFO – Philadelphia PHL – Zurich ZRH – PHL – SFO
Tue Jul10 – Thu Jul 19, 2018 (Google Flights link for calendar search).
American Airlines $436.11 round trip
San Francisco SFO – Madrid MAD – Basel BSL – MAD – SFO