Despite a setback after September 11th, travel advertising online soared in 2001. According to Jupiter Media Metrix' AdRelevance service, online advertising by the travel industry began a sharp increase in May with 291.9 million impressions and peaked in August with 1.1 billion impressions, a 263 percent increase. And although impressions plummeted the second week of September and bottomed out in early October, the industry has since returned to 94 percent of its pre-September 11th levels.

"The sector has showed incredible resiliency as booking services and airlines have turned to the Web to reach out to consumers during the busy holiday season," says Charles Buchwalter, vice president, media research, Jupiter Media Metrix.

Among the top ten online travel advertisers -- ranked according to their share of total travel impressions for the week ending Dec. 2, 2001 -- four are online agencies, making up 64 percent of the market, and three are airlines, making up six percent.

The top advertisers are: