The company, which tracks Web site visitors and other information, said U.S. travel e-commerce sales reached $103 billion in 2012, up 9 percent from the previous year. Air travel bookings, up 10 percent from the previous year, accounted for nearly two-thirds of all travel spending.
The data is the latest signal of just how many consumer tasks are moving online. ComScore noted that travel was a pioneer in the e-commerce category 15 years ago, and it's still growing at nearly double-digit rates each year.
As for the leading air travel providers, Southwest Airlines had the most page views, with 20 percent market share. It was followed by Delta and United Airlines.
Expedia ranked as the top site in the online travel agents category with 32 percent share, followed by Priceline at 17 percent and Orbitz at 13 percent.
Here's the overall breakdown: