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).
additional fare amount and change fees may apply cancellations within airline control air canada will rebook passengers on the next available air canada flight within seven days of the original travel date and they can also change the return to match the length of stay if necessaryancellations by traveler up to 24 hours after purchase air canada will cancel any ticket and perform a full refund without penalty beyond 24 hours voluntary changes to your itinerary may result in the imposition of additional costs or tariff upgrades