"The Web is extraordinarily well-suited to helping consumers make travel plans, and increases in home broadband penetration should continue to fuel growth in the online travel sector," said Sara Stevens, director of ComScore Travel Solutions, in the statement.

As the online travel industry has grown and matured, users have been slowly migrating from online agencies to airline, hotel or car-rental supplier sites, ComScore said. Even so, online agency and supplier sites are also growing. In 2005, agencies posted a 19 percent gain compared with 2004; suppliers recorded 21 percent growth, year over year, according to the study.

Over the past three years, online agencies have experienced greater competition from supplier sites in the airline and hotel segments and, to a lesser extent, in car rentals, ComScore said. Supplier sites, which accounted for 53 percent of airline ticket sales in 2003, captured 58 percent of airline ticket sales in 2005, according to the study. A similar pattern emerged in the hotel segment, where supplier sites grew from a 52 percent share in 2003 to a 59 percent share last year, ComScore said.

According to the survey, travel shoppers visit an average of three sites when planning leisure travel, mainly in search of the lowest prices. ComScore said 46 percent of respondents to the survey said the first site they visited was Expedia, Travelocity or Orbitz -- nearly double the proportion of people who reported starting their research at an airline, hotel or car-rental site.