  Social activities display bursty behavior characterized by heavy-tailed
inter-event time distributions. We examine the bursty behavior of airplanes'
arrivals in hub airports. The analysis indicates that the air transportation
system universally follows a power-law inter-arrival time distribution with an
exponent $\alpha=2.5$ and an exponential cutoff. Moreover, we investigate the
mechanism of this bursty behavior by introducing a simple model to describe it.
In addition, we compare the extent of the hub-and-spoke structure and the
burstiness of various airline networks in the system. Remarkably, the results
suggest that the hub-and-spoke network of the system and the carriers' strategy
to facilitate transit are the origins of this universality.
