I wouldn't know how to draft a rule (I don't even know if what they are doing is illegal). I think the Flights interface is superior to the competitors as well. However, it's unclear to what extent Google is using their control of ranking to ensure that their onebox shows up on top, and how much that prevents people from seeing competitor's sites.
I guess I find the question to be off point because when I search for flights from SFO to JFK I am looking for the ticket itself, not a fourth party that can resell the tickets to me. So all the links to Kayak etc are bad results anyway, although direct links to airlines' own sites would be good results. But that's essentially what Google Flights is: a vertical that cuts out middlemen.
If I search "sites that resell airline tickets" then Google Flights does not appear anywhere in the results.
