The holidays are obviously a big time of year for air travel, which means they’re also a big time of year for flight search. It seems only fitting that it is a good time for travel sites to complain about Google.

OK, that pretty much goes on all year ‘round.

Earlier this month, Google began showing its flight info (introduced back in September as the product of the company’s acquisition of ITA Software) right in regular search results for certain travel-related queries. Flight search was initially available via the left-hand navigation panel on Google searh result pages, but now these kinds of results are just the default search experience when Google thinks the users is looking for this kind of information.

“For example, if you search for [flights from San Francisco to Las Vegas] you’ll see a table that shows available flights, including duration and prices,” explained Emmet Connolly, UX designer on Google’s Flight Search feature. “You can adjust dates on the page, or click any flight to further research and book your trip.”

A new Wall Street Journal report says that the “top travel websites,” rely on Google for 10% to 20% of their traffic, citing Compete data, and that these sites are being pushed down Google’s SERPs in favor of Google’s own Flight search info. Obviously, they’re not happy about this.

There’s another interesting snippet from that report, talking about how Google said in talks with the Department of Justice around its ITA acquisition, that it would “build tools that drive more traffic to airline and online travel agency sites, and that competitors think Google is not living up to this promise. The report says:

Google acknowledges it has failed to make good on assurances it would link to the travel sites, but the company says it had no choice. “The airlines told us that they would not give us [travel data] if we provided booking links to” online travel agencies, Jeremy Wertheimer, ITA’s founder and now a Google vice president, said at an online travel conference last month.

It’s important to note that the DoJ did not require Google to link to the travel sites.

Google has been in antitrust discussions with regulators throughout the year, and last week, Senators Herb Kohl and Mike Lee put together a letter calling for an FTC investigation of Google, with an emphasis on the company’s search results. You can read that here.

Google paid $700 million to acquire ITA Software.