Google started to test a more advanced OneBox for flight-related searches. Right now, when you search for [flights from London to Barcelona] Google links to services like Expedia, Orbitz or Kayak. The OneBox is useful, but it doesn't show a list of flights.
After acquiring ITA Software, Google has access to a lot more information about flights and no longer have to send users to services like Expedia. Google can even provide information when you enter a vague query like [flights to Barcelona].
Here's the experimental flight OneBox, as spotted by Richard from SEO Gadget:
When you click "expand all non-stop routes to Barcelona", Google shows a very long list of cities. It's probably the biggest and most overwhelming Google OneBox. Maybe a drop-down would've been more useful.
After selecting one of the cities, Google sends you to a new search results page that shows a long list of flights.
It's nice to have all this information at your fingertips, but it's too overwhelming and these kinds of details aren't suited for an OneBox. Richard also noticed that "you get to data, with no call to action. I think this means most folks would be forced to repeat their search again on a flight provider."
Hopefully, Google will launch a Flight Search service that will also include the brilliant visualizations developed by ITA Software and the OneBox will just be a gateway to the new service.
{ Thanks, Richard. }