The Southwest Airlines Pilots Association and the Air Line Pilots Association have come to an accord in principle for a combined seniority list. The agreement governs how AirTran Holdings' pilots will be placed into the seniority list of Southwest Airlines. The list determines pilot compensation, routes and schedules. "It's really a big milestone for the pilots to come to this agreement in principle," said Paul Flaningan, a spokesman for Southwest. "It gives a signal to the other unions that everyone is moving forward with the integration."