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).
Here are some notes to keep in mind when changing or cancelling an flight: 1  Generally, you can cancel a flight booked through Expedia within 24 hours for a full refund. 2  Generally, changing a flight will result in you being charged fees by the airline. 3  Certain flights aren't subject to refunds.