The year 2007 was the first in which more travel was purchased online than off-line in the U.S., according to the PhoCusWright Consumer Travel Trends Survey.
The report predicted that "the gap between online and off-line will continue to widen as more and more travelers shift behavior to online shopping and buying."
The study said that 51 percent of U.S. travel was booked online in 2007, and it projected that percentage to increase to 56 percent in 2008 and 60 percent in 2009.
The survey also said that travel products with multiple components, such as vacation packages, are being purchased less frequently online, while simple components — plane tickets, for example — are being purchased more frequently.
The report also found that travel Web sites are evolving, with more of them offering features like group travel planning and booking, along with content generated by a community of readers and users.
PhoCusWright is a travel industry research company. The study was based on a variety of data, including surveys of travelers, interviews with travel executives and company reports.