That's interesting to watch... I didn't actually realize it would look so busy, but back in 1975 when I was in SFO airport, we had 5 major carriers departing San Fran to New York at 10 pm.. all flying a Boeing 747 or Lockheed 1011... I don't remember the configurations of the acft now, but that's roughly 2000 seats leaving at one time... plus there were 3 or 4 all cargo aircraft that also left at the same time, SF to NY.
30 years later I can see why it looks like a beehive.