[ricardo81]

It's (was in cases) a symbiotic relationship. Without sites offering flights, Google could have never offered relevant results to searchers in the first place. Same for any other vertical.

[amadeuspagel]

No google actually owns the backend of these flight search engines as well[1].

[1]: https://en.wikipedia.org/wiki/ITA_Software

[ricardo81]

In 2010 though, half into Google's lifetime and well into the time where they were dominant.