Many people will do things like use Google Travel to narrow down an initial set of potential flights based on times & cost, and then go to the individual airlines from there to book things. The GPs post is still a problem in this scenario.

Kayak has a flag to limit tickets shown to only those sold by airlines. That's the way to go.

That seems like a Google problem because of a poor interface. Unless you want each airline to standardize their offerings. Even then their would be differences based on loyalty programs, which airline you have a credit card for etc.

The legislation nor the regulations were geared toward third party aggregators.