The number of disruptive passengers is increasing in the friendly skies, according to a report from the International Air Transport Association.

The numbers, which were released back in 2017,  revealed that there is at least one unruly passenger for every 1,053 flights compared to the incident rate of one incident every 1,424 flights.

IATA categorizes unruly behavior in four levels:

Level 1– verbal aggression or failure to comply with crew instructions

Level 2- physical aggression or lewdness against fellow passengers or crew and damage to the cabin

Level 3- threats to life, and presenting of weapons onboard

Level 4- a breach of the flight deck (intended or unintended), an act of sabotage or a credible threat of seizing the aircraft.

According to the report, while incidents ranked in Level 1 and Level 2 categories are down, the number of incidents classified as Level 3 and Level 4 is on the rise.   

Level 3 incidents increased from 1% in 2016 to 3% in 2017, and Level 4 incidents more than doubled from 20 reported in 2016 to 50 incidents reported in 2017.

“Though Level 4 incidents are still extremely rare at 1% of all reported incidents – the severity of the threat cannot be ignored,” an analysis from the report reads.

The three most commonly occurring unruly behaviors include non-compliance with smoking rules (24% of all incidents), intoxication (27%), and failure to adhere to safety regulations (49%).

Despite the uptick, some passengers are able to get away with their behavior with no legal action thanks to a legal loophole.

As reported in Travel + Leisure, international airline regulation has a few loopholes that allow some passengers to escape law enforcement.

Under international law, officials in the state where the aircraft is registered have jurisdiction. In other words, unless a passenger commits an offense on an aircraft that registered to the destination, authorities have no power to proceed with the case. 

To address this, the IATA is hoping to pass a measure they call the Montreal Protocol 2014 (MP14).

The amendment was drafted in 2014 to close the “jurisdictional gap” by allowing law enforcement to deal with unruly behavior to the territory the aircraft lands in.

Right now, the IATA is calling on more countries to sign. The MP14 will take effect once 22 countries have signed on. Only 21 countries have signed thus far.