FlightRadar put together a fascinating one-minute clip of a full day's worth of flights on April 1, 2016. Out of the 164,209 flights tracked, 76,329 flew over the U.S! It's a must-watch.
Did you notice any significant saturation or gaps? FlightRadar explains (original source here):
"On the east coast, peak traffic activity takes place between 1000 and 1400 UTC (0600-1000 local). The west coast is particularly active from 0430—0800 UTC. At 0700 UTC much of the country is quiet except for the eastbound red eye flights making their way from the west coast to cities like New York, Boston, and Washington D.C." -FlightRadar
The study showed that the largest number of flights departed from Chicago O'Hare International Airport (approximately 1300), while the largest number of flights arrived in Hartsfield-Jackson International Airport in Atlanta (just over 1200). Most traffic, total? That'd be Chicago O'Hare.