With low-cost operations such as Southwest Airlines reporting profits and network carriers such as Delta Air Lines posting their smallest loss in two years, the airline industry improved its overall operating margins in the second quarter.

According to data released Monday by the U.S. Department of Transportation’s Bureau of Transportation Statistics (BTS), the network group managed a 0.5 percent loss margin in the second quarter – the seven straight quarter with a loss but the best quarter since September 2007.

American Airlines had a 5.3 percent operating margin loss, the worst in the group. American, the second leading carrier at Raleigh-Durham International Airport, lost $260 million in the quarter, according to BTS.

The low-cost group’s profit margin of 7 percent was its largest since the second quarter of 2007. The regional carriers’ profit margin of 7.2 percent was the largest since the fourth quarter of 2006.

Southwest Airlines, the leading airline at RDU, had a 4.7 percent operating margin on a $123 million profit.