DOW JONES NEWSWIRES U.S. airlines carried 3.9% more passengers in May than a year earlier, as airlines continued to boost capacity to meet rising demand, the Department of Transportation said. The latest increase reflects an ongoing recovery in air-travel demand. Airlines have widely benefited from such conditions, which have allowed them to raise fares, but have also felt mounting pressure as higher fuel costs weigh on their bottom lines. The DOT's Bureau of Transportation Statistics said airlines carried 63.8 million passengers in May. Traffic climbed 4.2%. Load factor, a measure of plane fullness, rose to 83.6% from 82.3%, as capacity grew 2.6%. Delta Air Lines Inc. (DAL) carried the most total and international fliers, while Southwest Airlines Co. (LUV) remained the top domestic carrier. Atlanta Hartsfield-Jackson International Airport led in total passengers, while Miami saw the most international fliers board. -By Drew FitzGerald, Dow Jones Newswires; 212-416-2909; andrew.fitzgerald@dowjones.com