Get round-trip flights on Southwest Airlines with rates from $126 on Airfarewatchdog. We found the lowest fares on flights between Chicago and Detroit with at least 21 days advanced booking. Fights from New York to Atlanta start at $138, and flights from Seatttle to San Diego start at $168. You can enter your own travel dates and locations to find fare prices on Airfarewatchdog. Many of the best prices we found need to be booked months in advance and require travel on specific days of the week. Taxes, fees, and restrictions may apply.