United Airlines

Phoenix to Barcelona or Madrid United $508-$568 Jan-April

LAX/SFO to Barcelona $433-$513 Star Alliance/Oneworld Jan-May

Fare Alert Boston to Copenhagen $265-$335 Air Canada, London $416-480 United/Delta all summer

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Fare War $343-$444 Boston to Barcelona, Madrid and around Spain Jan-May

United $478-$498 San Francisco to Beijing nonstop November to April 29

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Fare Alert Los Angeles to London $535-$557 AA/DL/UA nonstop Jan-May

Phoenix to Spain $548-$600 DL-UA Barcelona, Madrid and more

Newark to Paris $470, Rome, Barcelona, Madrid $499 United-Star Alliance Jan-May

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Portland PDX to London United $555, Amsterdam UA $580, Delta $571 Dec-May

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AA/DL/UA Denver to Paris $448, Amsterdam $444, many cities $431-$544