Looking to invest in an airline that has solid earnings growth, double-digit percentage traffic growth, good control over costs and isn't named JetBlue ( JBLU) or Southwest ( LUV)? Consider Mesa Air Group ( MESA), a small regional carrier operating out of Phoenix, serving 150 markets as a code-share partner for big guys like America West ( AWA) and US Airways. Last week, the company announced second-quarter earnings that handily topped Wall Street estimates and on Wednesday, it said traffic was up 31% in the first four months of 2003. Savvy investors already have caught on to the Mesa story, doubling the stock since it hit $3 on March 13, when it was depressed by war fears. But even after the move, long-term buyers could see additional upside as the company continues to move away from unprofitable turboprops and into the regional jets that its larger partners prefer.