On a flight from Reykjavik bound for New York last Thursday, an unruly passenger was zip-tied and duct-taped to his seat as well as across his mouth. According to a report by CNN.com, flight staff restrained the passenger who was “hitting, screaming and spitting at other passengers, while yelling profanities,” the airline spokesperson told CNN. The use of duct tape and plastic zip-ties as restraints was standard protocol for the airline.

Can airline staff legally restrain unruly passengers aboard flights? The answer is yes. If the passenger is jeopardizing the safety of crew or other passengers and received warnings to cease their behavior, and/or the passenger is/has committed a crime, flight personnel may restrain the passenger.

SEE ALSO: Airline Diverts Aircraft During Solar Storm

With no police in the air, airline staff are responsible for flight safety. If a passenger becomes unruly and use of force or restraint is necessary, flight crew and even other passengers themselves have worked together to keep troublesome fliers under control. Once the passenger has been restrained, local authorities are contact by flight staff to take over upon landing.

Although reports of airline misconduct certainly resonate with passengers, a report from NASA’s AMES Research Center detailing instances of disruptive customers on flights show just what airline staff have to put up with on a bad day. Within the reports, flight attendants in particular have dealt with everything from dog attacks, passenger violence, theft and more. In response, passengers have been restrained and even handcuffed for the duration of flights.

As shown by the flight aboard Iceland Air, international flight crews are also able to detain passengers. Transportation bureaus in nations outside the United States provide their own guidelines for dealing with such troublemakers. Transport Canada, for example, has a brochure (PDF) for how flight crew should deal with unruly passengers, explaining that “use of force” should be the last available option and describing how attendants can collect evidence if a crime has been committed.

SEE ALSO: What Happens If You Get Sucked Out of a Plane?

Private associations of airline personnel also issue their own guidelines to crew members for dealing with disruptive fliers. The U.K. Flight Safety Commission, for example, assembled an extensive guide (PDF) for dealing with problem passengers, including tips for preventing an incident and detailing different approaches for different situations.

When flight crew do resort to restraining passengers physically, it tends to be for extreme situations, as was the case with the Iceland Air flight. Last September, a passenger aboard a United flight was restrained with belts after repeatedly sexually harassing and attempting to assault women aboard the flight. The following month, a drunk man coming off a 50-day bender was restrained aboard a flight after attempting to open the airplane door during descent.

Flight crew can be equipped with handcuffs or other restraints, but the Iceland Air flight wasn’t the first time that attendants have had to get creative. In 2008, a woman bound for a flight to North Carolina was duct-taped after she began physically assault crew and other passengers, and ankle cuffs failed to restrain her sufficiently.

Although these episodes may make the situation appear as though disruptive customers are increasingly common, according to the Federal Aviation Administration, instances of unruly passengers have decreased to 131 in 2011, down from a high of 330 in 2004.