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).
If you cancel a flight: If you decide against making a trip on a non-refundable ticket, the airline owes you nothing. You are out the cost of a ticket or at least an expensive change fee â although some airlines will make exceptions in cases of death or illness. You must contact the airline to learn your options.