Following in United's jetstream, US Air will begin charging $25 for a second bag weighing no more than 50 pounds. This applies to all economy class fares, even full fare ones, with the exception of those bought by upper tier frequent flyers. Some other exceptions apply, such as military and unaccompanied minors. The fee goes into place for travel on or after May 5, 2008. We expect other airlines to add a secon bag fee in coming weeks. So pack light or pay the piper.