Airplanes emphasize inequality. Flights where coach class passengers board by walking through first class have 3.84 times higher rates of air rage. Seeing the disparity evidently emphasizes any discomfort felt in coach. That 3.84 increase is an average. Within coach there’s a 2.8-fold increase. When coach passengers walk into first class during a flight, there’s an 11.86-fold increase.
(Click on the photo for the link.)

“Economy Passengers May Rage After Being Marched Through First Class” – Ars Technica