CNN is on 24/7 is all of the airports I frequent.
That linked source seems suspicious to me and I read the comments.
I work in the TV news business. No, not for CNN, locale stuff. Those numbers are from Nielson. Dont be afraid of the facts! FNC is still the dominant news network when it comes to moulding opinion. FNC fans watch for longer durations because FNC is opinion-heavy, lots of analysis, pundits, etc. CNN scores an overall higher audience because it gears its programming to blurt out basic facts in short periods of time, so it attracts people who are on the go, who dont have a lot of time to sit down and watch anything in-depth.
The Airport thing: Airport coverage isnt included in Nielson stats, nor any other business that may have televisions streaming news channels. You cant gage for audience since you have no idea who's stopping to watch and who's just walking by.