Evan Schuman's StorefrontBacktalk

As the summer vacation season has arrived, travel web sites are getting a serious workout. Perhaps a bit too serious a workout, according to one uptime monitoring service, which reports that one site had 2-and-a-half hours of downtime.

Although the survey looked at 16 major travel sites?including Orbitz, Travelocity, Yahoo and Priceline?Expedia was not among them. Why not? Expedia’s system apparently didn’t take kindly to being watched and blocked the nosey system inquiries from report conductor Pingdom.

“Expedia.com was originally part of the survey, but the results have been omitted because the service blocked monitoring during part of the test and the results would therefore not be fair,” Pingdom said in a statement.

Pingdom analyst Peter Alguacil said Expedia’s blocking could have been accomplished any one of several ways. “It could have been an automated security feature that was activated after a certain amount of time by too many accumulated visits from our servers,” Alguacil said, “or they could possibly have done it manually?by configuring firewalls, for example. Monitoring is performed from a number of servers, so all they have to do is block those specific servers from accessing their website.”

As for the sites that were tracked, Pingdom considered a site “down” when it either replied with an error or didn’t reply at all within 30 seconds. OneTravel achieved that for 150 minutes and fared the worst. Others included: Kayak.com (94 minutes); Hotwire (85 minutes); StaTravel (66 minutes); Quikbook (34 min.); Travel.Yahoo.com (11 min.); CheapTickets (six min.); Travelocity (five min.); Orbitz (five min.); TravelZoo (five min.); Hotels (five min.); and SideStep (five min.). The site also tracked Travel, Priceline, Site59 and LastMinuteTravel, all of which were found to have no downtime during the four-week-long test period from May 22 to June 19.