Catch the earlier flight, minus the fee

Q. Which airlines do not charge a fee for flying stand by on an earlier flight?  I occasionally get to a connecting airport and have the time to make an earlier connection, however, I always get the "well, for $50 you can fly earlier..."  

A. As we read the rules, Airtran, JetBlue and US Airways will allow you to take an earlier flight on the same day, on a non-confirmed standby basis only, without charge. However, most airlines now charge a fee, typically $50 for domestic flights, if you wish to change your flight on the same day of travel and get a confirmed seat. Southwest Airlines’ official policy is a bit different: there’s no “charge” as such to change your flight, but you’re supposed to pay the then-current last minute “walk up” fare (so if your original fare was $39 and the current last minute fare that day is $109, you’ll pay the $70 difference). We’ve heard, however, that Southwest ticket agents often “neglect” to collect the fare difference.