The topic is introduced in a MIT Technology Review article (above title), with links to the academic paper and pdf file. A summary within the article and paper:
"The first is through each plane’s flight schedule from one destination to the next–a delay in one leg naturally propagates to the next.
The second comes from passenger and crew connections. Clearly, an aircraft cannot take off if the crew are delayed on another flight.
Finally, there is airport congestion. A given airport can handle only a certain rate of take offs and landings and becomes congested when numbers rise beyond these levels.
However, Fleurquin and co conclude one of these factors is far more damaging than the others. “Our simulations evidence that passenger and crew connections is the most effective single mechanism to induce network congestion,” they say."
The paper is 6 pages long, technical, and with 12 pages of notes and appendixes. I will finish reading and add a few comments later. This is outside my field of understanding, but think I can slog through it. Hope some experts here will too.