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 decide to no longer travel either because your original flight was canceled or you are delayed two hours or more, you can receive a refund to your original form of payment. Other optional services such as checked baggage and Economy PlusÂ® can also be refunded, but ticketing fees (such as those for making a reservation in person) are not.