Google has been taking a lot of heat for placing Google Flight Search results above all organic results, but although Bing has largely flown under the radar, it takes preferencing even a step further than Google does.
If you merely enter "JFK to LA" into the Bing search box, then Bing's auto-suggest feature produces its own Bing Travel result as the first suggested query, like this:
And, if you select that first link, as many users would, it takes you directly to Bing Travel -- and thus it bypasses all other sponsored and organic results on the traditional Bing search results page.
Even Google, which has been lambasted by critics, including some US Senators, for the preferential and self-serving way it handles flight search, doesn't go as far as Bing does in skewing flight results in its own favor.
If you enter "JFK to LAX" into the Google search box, Google Instant immediately produces Google Flight Search results above all organic results, but at least Google also shows organic results on the first screen from Kayak and Expedia, for example. Google handles the flight query like this:
If Bing users ignore the auto-suggestion of navigating directly to Bing Travel and select the "JFK to LAX" query, then Bing displays Bing Travel results as an Instant Answer (as it does for shopping, local, movies, weather and stock quotes) above all other organic results.
Bing's Instant Answer for flights is similar in some ways to Google's Flight Search results on their respective search results pages, although Google's offering is tilted much heavier toward airline websites than is the Bing Travel solution.
Bing Travel flights, which is powered by Kayak, offers results from online travel agencies and airlines while Google Flight Search has shut out OTAs and other metasearch companies, such as Kayak.
Still, Bing, with its auto-suggestion of Bing Travel as the first query, is taking the biasing of flight search results to new levels -- even one-upping Google in this regard. With Bing you can bypass the search results page altogether and navigate directly to Bing Travel while Google at least delivers users to a Google search results page, where they can view other companies' results, too.
Still, Bing has escaped much criticism for the preferential way it treats flight -- and other -- search results, probably because of Bing's relatively low search-market share.
And, FairSearch, which has led the protest against Google's search engine practices, is quick to criticize Google's practices and its "monopoly power," but doesn't seem to be particularly incensed over how Bing processes flight-search results.
Fair or unfair?
It should be pointed out that Microsoft, which operates Bing, is a key member of FairSearch.
On the Bing issue, FairSearch states:

Only Google has the monopoly power in search to tilt the market in an unfair way by steering consumers to its own services and away from all alternative, competing providers, depriving consumers of the benefits that flow from a truly competitive market.
It's a well established principle of antitrust law that some tactics that are illegal when employed by a dominant power in a market are not when employed by a company that lacks that power in a market controlled by another party. If Google was not the dominant power in search and search advertising, and already found to have monopoly power by authorities who enforce antitrust law, it would not be the subject of scrutiny and investigations around the world.
What's at stake in online travel is whether Google will be allowed to use its monopoly power in search and search advertising to unfairly get a leg up in that space rather than compete on the merits and give its own search engine users the choice between what Google has to offer and what sites like Kayak, Expedia and Travelocity have to offer.
Consumers win when they get to pick winners and losers, not Google.
And, when pressed again about its silence about Bing's practices, FairSearch adds: "FairSearch has been focused on the threat to consumers and a well-functioning free market from Google's abuse of its monopoly power in search and search advertising since day one. If Google lacked monopoly power, it would not have the ability to unfairly distort the market in ways that limit consumer choice and deprive them of the benefits that a free market brings."
However, despite Bing's Teflon (nonstick) status so far, the way Bing positions flight search queries and results certainly wouldn't escape the attention of the US Federal Trade Commission, which is investigating Google's practices.
Despite Bing's relatively weak sway in the market, it's only a matter of time before things heat up for Bing, as well.
Google declined to comment on the issue, and Microsoft didn't immediately respond to a request for comments.