The Mississippi River is known as the Middle Mississippi from the Upper Mississippi River's confluence with the Missouri River at St. Louis, Missouri, for 190 miles (310 km) to its confluence with the Ohio River at Cairo, Illinois. The Middle Mississippi is relatively free-flowing.
As Hopper notes, eight major U.S. airlines offer free cancellation for tickets purchased at least seven days in advance: Delta, United, US Airways, JetBlue, Southwest, Spirit, Frontier and American (in American 's case, you'll hold your ticket instead of purchasing it).
Step 1. Cancel within 24 hours to lessen the chance of a fee. According to Susan Stellen of the New York Times, Although Expedia, Orbitz and Travelocity do not allow you to put a reservation on hold, all three allow customers to cancel an airline ticket purchase within 24 hours after booking and get a full refund..