A research study examined data from millions of plane flights to determine possible indicators for incidents of air rage—when passengers become unruly or violent in some way. The study found that flights that have a first class or business class cabin and a separate economy class section are more likely to report incidents of air rage than flights with only one class of seats.

The study also showed that when flights board from the rear of the aircraft, rather than inviting first class passengers aboard first, there were fewer incidences of unruly behavior. When people walk past passengers in the first class or business class cabin and see them swilling champagne and eating caviar, they feel as if they have been treated unequally and unjustly.

The envy and jealousy make passengers more prone to feel justified losing control and acting rudely or violently.