WASHINGTON (AP) — Incidents of unruly passengers on planes are increasing, and more effective deterrents are needed to tackle the problem, a global airline trade group said Wednesday.

There were 10,854 air rage incidents reported by airlines worldwide last year, up from 9,316 incidents in 2014, according to the International Air Transport Association. That equates to one incident for every 1,205 flights, an increase from one incident per 1,282 flights the previous year.

A majority of incidents involved verbal abuse, failure to follow crew instructions and other anti-social behavior. Eleven percent included physical aggression toward passengers or crew or damage to the plane. Alcohol or drugs were a factor in 23 percent of the cases, although in the majority of incidents the drugs or alcohol was consumed prior to boarding, the association said.

Training staff in airport bars and duty-free shops to sell alcohol responsibly, including avoiding offers that encourage binge drinking, can cut incidents by half, the association said, citing an initiative by Monarch Airlines at London's Gatwick Airport.

Airlines also want more countries to ratify a 2014 treaty that closes gaps in laws for dealing with unruly passengers. So far, only six countries have ratified the pact.

"More are needed in order to have a consistent global approach to this issue," said Alexandre de Juniac, the association's director general.