Using the above route, how long will the journey take?
Aer Lingus flies direct to both San Francisco and LAX, with pre-clearance in Dublin airport. It takes just under 11 hours. It will take you about an hour to fly between LAX and San Francisco.
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Aer Lingus flies directly from Dublin to San Francisco. The flight time is 11 hours and 5 minutes. This non-stop flight departs from Dublin at 12:30 pm and arrives in San Francisco at 3:35 pm. Dublin is 8 hours (time difference) ahead of San Francisco.
Just in case you're wondering, according to Momondo, the cheapest day to fly is on a Thursday and Sundays happen to be the most expensive.
Besides Aer Lingus, you can check out Delta (one stop in New York JFK) or KLM (one stop in Amsterdam) flights. Total time including stopover is around 15 hours. The stopover in New York is just over an hour. You'll have enough time to connect to the next flight since preclearance procedures are done in Dublin. For additional information on US preclearance in Dublin airport read this article: https://www.dublinairport.com/at-the-airport/passenger-information/us-preclearance-facility
Shaun - I would talk to the airline. It all depends on who you fly with and where you originate, etc. The local airline offers quite a bit of deals during the year, and some Black Friday specials, etc. Happy hunting.