U.S. online travel agency bookings will likely fall for the first time in 2009, according to a report by online travel research firm PhoCusWright.

PhoCusWright said the combination of a slumping travel industry and a maturing segment will cause a drop in airline and hotel reservations by the major OTAs.

While online agencies’ share of the approximately $230 billion expected to be spent on U.S. travel this year will rise about 2 percentage points, to 15%, OTA bookings will fall 3% this year, to about $35 billion, PhoCusWright said.

The decline marks a first for the segment, which has been losing ground to hotel and airline websites: The OTAs’ share of online travel bookings has fallen to 39%, from a peak of 53% in 2002.

But OTAs have continued to build bookings because of the growing popularity of using the Internet to make travel plans. Overall, online travel bookings have more than tripled over the same time period.

"Airlines and hotels have been very effective with mechanisms to drive a lot of leisure business travel to their websites," said Douglas Quinby, senior director of research at PhoCusWright.

"This year, online travel is effectively a mature market, so when the total travel industry now gets sick, online travel is certainly going to catch a cold," he said.

Last week, Expedia, which has about a 40% share of the U.S. OTA market, said year-to-date domestic bookings were down 2.7% from a year earlier, to $11.6 billion.

Still, OTAs are outperforming the overall market because younger, bargain-hunting travelers, who are more typical OTA customers, have cut back travel spending less dramatically than older travelers, who more regularly use travel agencies or call in for their travel reservations, Quinby said.

Additionally, OTAs next year will likely benefit from what Quinby said would be a slight rebound in travel spending that will accelerate in the later half of 2010. Overall U.S. travel spending will rise 1% next year, while online spending will increase 5%, PhoCusWright said.

"The online travel agencies have gained back share since eliminating booking fees," said Forrester Research analyst Henry Harteveldt. "So for price-sensitive travelers, that’s enough to keep them on the site."