The top airline websites, ranked by visitors, are successful in converting visitors to buyers, writes Internet Retailer, citing a new report on travel websites by Nielsen/NetRatings. Southwest Airlines, ranked first with a unique monthly audience of 8.14 million, enjoys a conversion rate of 14 percent. In second place, American Airlines, with 5.6 million unique visitors, has a conversion rate of 9 percent. Delta, third with a monthly audience of 4.9 million, has conversion a rate 10 percent.

Online travel agencies attracted twice the number of visitors as airlines during April, but had half the conversion rate. Expedia led with 16.3 million unique visitors and a conversion rate of 5 percent. Travelocity was second, at 11.7 million and 3 percent, and Orbitz ranked third with 11.6 million and 4 percent.

Nielsen also reports that nearly 50 percent of all airline ticket sales and reservations were conducted exclusively online during the last six months.