Air rage is getting uglier.

As the number of serious incidents involving drunk and violent travelers increases, airlines are being forced to physically restrain an increasing number of disorderly passengers, according to the International Air Transport Association.

In some cases, the conflicts erupting in airplanes have hurt carriers’ own reputations, such as when security personnel dragged a passenger from a United Airlines plane because he refused to relinquish his seat. Chief Executive Officer Oscar Munoz apologized for how the company handled the episode.

The number of incidents involving disorderly passengers has risen in recent years, with IATA saying in the past that airlines are increasingly having to navigate local laws to bring prosecutions for offenses and crews have to be trained on how to handle violence.

While the total number of reported incidents last year actually fell by almost 10 percent to 9,837, the portion that were deemed a higher risk increased from 2015. Here’s what unruliness looked like last year:

• An incident was reported every 1,434 flights
• 12 percent included physical assault, up from 11 percent a year earlier
• About a third of all incidents, involving 3,288 passengers, were related to intoxication, including 444 registered as cases that escalated physically

IATA said the more than half of safety rules-related offenses involved passengers smoking on board, either in the main cabin, or more likely, in the bathrooms.

The figures accounts for 190 of the world’s airlines so “are likely to significantly underestimate the extent of the problem,” IATA’s assistant director for external affairs Tim Colehan said in Geneva.