The number of unruly passenger incidents in 2016 that went into the International Air Transport Association (IATA) logbook may be misleading.
Last year, airlines reported 9,837 unruly passenger incidents, a slight drop from the 10,854 incidents reported in 2015, according to a newly released report by IATA.
But the global airline industry body believes that carriers have under-reported instances that disrupt flight experiences and travel plans of countless other passengers and adversely impact the workplace for cabin crew.
Tim Colehan, IATA's assistant director or external affairs, said the 2016 figures did not give a true picture as only 190 airlines shared their information with IATA for analysis of incidents.
There are over 5,000 airlines around the world and more than 270 of them are IATA member airlines, not all of which participated in the reporting of unruly and disruptive passengers.
"So if anything, the statistics are likely to significantly underestimate the extent of the problem," Mr Colehan said.
Between 2007 and 2016, more than 58,000 unruly passenger incidents were reported to IATA, underscoring the significance of the issue.
However, the reported incidents in 2016 equated to a rate of one incident report per 1,434 flights, compared with one incident per 1,205 flights in 2015.
There are more than 100,000 daily flights globally.
There are two levels of disruptions.
There was a small increase in the proportion of the more serious level two incidents -- physically abusive or obscene behaviour, verbal threats of physical violence and tampering with emergency or safety equipment -- from 11% of incidents in 2015 to 12% in 2016.
The vast majority of incidents were classified as level one, which tend to be mainly verbal in nature, at 87% compared with 88% in 2015. These misbehaviours include failures to follow crew instructions or violations of a safety regulation including smoking in toilets.
In many cases these incidents can be managed to a satisfactory conclusion by crew using de-escalation techniques, according to Mr Colehan.
That said, there was also an increase in incidents where after all other forms of de-escalation techniques had been exhausted, the cabin crew had no other option but to restrain the unruly passenger for the safety of everyone on board, he said.
In 2016, 169 reported incidents ended with unruly passengers being restrained, a jump from the 113 reported in 2015.
On closer look, IATA found that most of the incidents of passenger misconducts were related to people who were intoxicated by alcohol or narcotics.
The two other most frequent issues were not complying with smoking regulations and other safety rules followed by disputes between passengers.
Mr Colehan said the intoxication issue related to drinking prior to boarding the aircraft or on-board consumption of duty free alcohol without the knowledge of the crew.
The level of intoxication may not be apparent at the time of boarding.
Further analysis of intoxication shows that the majority of incidents were level one, but 444 were level two, a third of which involved intoxication.
Despite the slight drop in reported incidents, IATA said the statistics highlight the need for governments, airlines, airports and other related companies to continue to implement a strategic approach.
That calls for governments to play their part by improving international legal deterrent.
Airports, airport restaurants and bars and duty-free shops have particularly important roles to play to ensure responsible sales, marketing and promotion of alcohol to avoid incidents that involve intoxication that have to be dealt with during a flight.
Mr Colehan identified legal jurisdiction as the biggest problem that results in passengers involved in serious unruly behaviour during a flight often facing no charges when the flight lands.
This is because under existing international laws, it is the authorities in the country where the aircraft is registered that have jurisdiction over an incident that takes place during a flight. When the aircraft leaves one country and lands in another, authorities on the ground are often powerless to take action.
IATA is counting on the Montreal Protocol 2014 (MP14) as a solution of this issue by giving the "State of Landing" the legal jurisdiction to deal with the passenger. This, the airline industry body believes, will be a stronger deterrent through better enforcement.
Twenty-two countries are required to adopt the protocol to put the rules into force. So far, 12 have done so and IATA hopes the international aviation treaty will be fully ratified by 2019.
