So the aeroplane was en-route from LAX to ORD. The fighters that scrambled were heard going supersonic by a lady in Barrington (which is very close to ORD). The intercept must have been very close to Chicago.
Good job nobody "twitched" and thought the airplane was "threatening". Although we will tend to think this was a minor incident a slight breakdown in communication in this time critical situation could easily have resulted in this aircraft being shot down.
Good job the pax got involved. Well done to them. Hope we are so fortunate next time.