American Airlines, AirTran Airways, Continental Airlines: $15 for the first checked piece of luggage, $25 for the second.
Alaska Air: Passengers traveling on tickets purchased before May 1, or for travel before July 7, can check one bag for free. The second bag is $25. Beginning July 7, Alaska is adding a $15 charge for the first bag.
Delta Air Lines and Northwest Airlines: $15 for the first, $25 for the second. For international tickets, the first two checked bags are still free. But for flights to Europe, Delta and Northwest are adding a $50 charge for the second checked bag beginning with tickets bought May 23 for travel beginning July 1.
JetBlue Airways: First bag is free, $20 for the second.
Southwest Airlines: FIRST TWO BAGS ARE FREE.
United Airlines: $15 for the first, $25 for the second, if paid online. If paid at the airport, United adds an extra $5 for tickets purchased beginning May 14.
US Airways: $15 for the first, $25 for the second. Beginning with flights on July 9, US Airways will add $5 if the fee is paid at the airport for tickets purchased beginning April 23.
Note: All charges are for domestic flights, except where noted for Delta. The charges generally don't apply to first-class or business-class travelers, high-level frequent fliers and some other categories of passengers, such as active-duty military personnel.