Mobile sites in the travel industry received 75.4 million monthly unique visitors in July 2013, according to web and mobile measurement firm comScore Inc. The mobile site of TripAdvisor Inc. topped the mobile travel list with 15.4 million unique visitors during July, though TripAdvisor is an informational site not a commerce site. Most travel sites measured by comScore are mobile commerce sites where consumers can book accommodations or airline tickets.

Following are some of the most highly visited mobile sites in travel and their monthly unique visitors in millions for July 2013, according to comScore:

• TripAdvisor, 15.4
• Expedia Inc., 12.2
• Priceline.com Inc., 7.5
• Southwest Airlines Co., 6.9
• Travora Media, 5.2
• Orbitz Worldwide, 4.0
• Delta Airlines, 3.9
• Marriott, 3.6
• Hilton Worldwide, 3.2
• Kayak.com, 3.2
• USA Today Travel, 2.9
• Travelzoo, 2.6
• Travelocity, 2.6
• Yahoo Travel, 2.5
• About.com Travel, 2.4
• HomeAway, 2.2
• Disney Parks and Travel, 2.2
• Choice Hotels International, 2.1
• JetBlue Airways, 2.0
• InterContinental Hotels Group, 2.0

Many of these same sites are at the top of the list for desktop traffic, although TripAdvisor leapfrogs Expedia for the No. 1 position in mobile, says Andrew Lipsman, vice president of industry analysis at comScore.

“This speaks to the utility of a travel information site when people are traveling from place to place and looking for information, recommendations and reviews,” Lipsman says. “Online travel agencies still perform well on mobile, as they do on desktop, with price comparison for airfare and hotels always one of the most important drivers of online travel behavior. Leading hotel sites also become somewhat more popular on mobile because people are perhaps more likely to engage with the brands during a stay, and because hotel Wi-Fi networks often initially direct mobile devices to a hotel site.”

Comparing the travel industry to retail, it turns out that mobile commerce is bigger in retail. In July 2013, 45% of minutes spent with online retail was on mobile devices while only 25% of minutes spent with online travel was on mobile, comScore finds.

“It seems there’s an untapped opportunity for travel to become even more mobile-focused because its content can be especially useful and relevant for people when they are travelling,” Lipsman says. “Travel apps are not downloaded as readily as retail apps because the average person shops a lot more frequently than they travel, and frequency of usage often drives app download behavior.”