For the first time last year, more travel was purchased online than off-line in the US, according to thePhoCusWright Consumer Travel Trends Survey.

"The gap between online and off-line will continue to widen as more and more travelers shift behavior to online shopping and buying," predicted the report.

The study said that 51% of US travel was booked online in 2007, and it projected that percentage to increase to 56% in 2008 and 60% 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.

Report by David Wilkening