It looks like this is not the fastest commercial flight but the fastest subsonic flight. The Blackbird and Concord records you are talking about are a different category.
The entire reason a subsonic flight could go at speeds normally only possible to supersonic aircraft, is because of the speed of the jet stream driven by Ciara. The plane is flying at subsonic speeds within a moving pocket of air that adds quite a lot to that speed. That's the interesting part about this story.