Originally Posted by Ftrooppilot

First you have to look at how the government defines a regional airline.

A U.S. airline's rank is determined by the amount of revenue it generates.

Large regionals - These are scheduled carriers with $20-million to $100-million in annual revenue. They operate aircraft that can accommodate more than 60 passengers. [NOTE: No upper limit on # of seats. Air Tran, American Eagle, Comair, Mesa, Express Jet, Sky West and others are (by government definition) National Airlines - not Regional.]

Medium regionals - These airlines operate on a smaller scale, with operating revenues of under $20-million, and often use only small aircraft.

Small regionals - These airlines don't have a set revenue definition, but are usually referred to as "commuter airlines." They use small aircraft with less than 61 seats.

Regional aircraft are so defined by the manufacturer. (ERJ, CRJ, etc.)