United Airlines Mileage Plus
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Buy miles United 50% bonus to March 31

AA and UA LAX-Philadelphia $108 to $117 each way April-May

United or American Baltics to USA $330 New York to $499 SFO or LAX round trip

All alliances $571-$604 LAX or SFO to Rio de Janeiro GIG April-June 2016

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United Airlines $78.20 round trip LAX–Chicago ORD Apr-May 2016

American $83 each way Las Vegas to Philadelphia April-May 2016; United $87

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United $88 each way San Diego to New York LGA April-May 2016 and several other low fares

Air China $621 LAX-Singapore earns 100% Mileage Plus flight miles April-May 2016

Alaska or United $108 each way LAX to Baltimore BWI nonstop in April-May 2016

United/Avianca Bogota to Beijing $340 round trip