Several prominent web travel sites—including Expedia, Hotwire, Kayak, and Travelocity—have banded together as Fairsearch.org and petitioned the US government to block the $700 million sale of ITA to Google. ITA is a back-end airfare-reservation system used by these and many other services, and the companies opposed to the deal believe that if Google is allowed to purchase ITA, Google would have too much control over the online travel market.

Google announced its intention to purchase ITA in July. The US Department of Justice (DOJ) is currently undergoing an extended antitrust review of the deal.

"Acquiring ITA Software would give Google control over the software that powers most of its closest rivals in travel search and could enable Google to manipulate and dominate the online air-travel marketplace," the companies wrote in a press release announcing their opposition. "The end result could be higher travel prices, fewer travel choices for consumers and businesses, and less innovation in online travel search."

ITA provides the technology used by 65 percent of all carrier-direct online flight searches in the United States and is used by 6 of the top 10 airlines, including American, Continental, Southwest, United Airlines, US Airways, and Virgin Atlantic.

At issue is the fact that Google is already responsible for 30 percent of all search-engine traffic to online travel sites—far more than any other search engine. If Google is allowed to purchase ITA, the companies say, it will dominate the market for online travel search and "could use ITA Software to stifle competition in online flight search and to extend its dominance in Internet search into search for online travel, which is the largest segment of e-commerce." (Google controls over 70 percent of all search traffic in the United States and owns over 77 percent of search advertising.)

Microsoft has separately opposed the deal, as well, and has had conversations with DOJ investigators about the potentially devastating effects the deal could have on the travel industry. Microsoft's Bing search engine also uses ITA for its travel-related services.

Notably, not all travel services oppose the deal. Priceline, Travelport, and Orbitz have offered "qualified support" for the deal, and no major airlines have spoken publicly one way or the other—at least, not yet. Privately, some airlines apparently oppose the deal.