Delta said total ticket sales from January through August at Delta.com were more than $1 billion. The site now accounts for more than 12 percent of the airline's total ticket sales, the company said.
Delta isn't the only airline pushing its online site. At Southwest, for instance, around 46 percent of revenue in the first quarter of the year originated at the company's Web site.
The airlines want travelers to head to their Web sites, instead of to online or offline travel agents, for one reason: money.
It costs Delta about $1 to book a flight through its Web site, compared to between $12 and $17 when a flight is booked through an online site such as Expedia or Travelocity, said Henry H. Harteveldt, senior analyst at Forrester Research.
"It's very clear that the airlines are doing everything they can, and Delta is at the forefront in driving customers directly to their site. Delta has been the most creative, " he said. For example, he cited promotional incentives such as "fan fares," which let customers fly at discount to follow sporting teams around the country.
Airlines have been looking for other ways to save cash. Several, including Delta, haveon paper tickets, pushing travelers to use electronic tickets, which cost less for the airlines to process. Delta said electronic tickets now account for about 80 percent of its tickets sold worldwide.