United Airlines has San Francisco to Quito, Ecuador at $444 round trip for travel October to April. There are only a few dates each month with these low ticket prices. United is more than $100 lower than American or Delta. JetBlue has comparable fares to United on fewer dates.
San Francisco SFO – Houston IAH – Quito UIO – IAH –SFO
Sunday Feb 4 – Tue Feb 13
Momondo shows UA tickets at $426 round trip for these dates.