Call it workplace violence at 30,000 feet. Or “sky rage.” Unruly airline travelers shouting at, kicking, punching, or threatening flight attendants, and even storming the cockpit, is a hot news story and reportedly a growing trend. For airline crews this “at-risk” behavior can be a serious job hazards.

This summer, the Association of Flight Attendants, AFL-CIO, held a “day of action” against air rage, handing out passenger education leaflets at four U.S. airports. Earlier this year, the union successfully pushed Congress to increase penalties for unruly passengers. Fines have been raised from $1,100 to $25,000 for passengers who assault flight attendants.

And the U.S. Attorney General can now deputize local police so they can detain problem passengers once a flight lands. (In the U.S., aviation comes under federal jurisdiction, and in the past arrests could only be made by a federal agent from Customs, Immigration, or the Secret Service.)

Airline industry officials and union leaders disagree over the size of the “air rage” problem. Last year, the Federal Aviation Administration brought 140 cases of crew member interference against passengers. Airlines claim serious incidents are very rare. British carriers transported 85 million travelers in 1998, with only about 100 extreme cases of violent behavior reported, for example.

But at an International Air Transport Association meeting, it was reported that air rage incidents have increased by 400 percent since 1995. It’s enough of a problem that airline insurance firms offer “interrupted flight insurance” to cover the cost of unscheduled landings caused by incidents of air rage.

There’s no dispute that extremely agitated air travelers jeopardize the safety of crews and passengers. A recent NASA study found in 40 percent of 152 cases of air rage, pilots either left the cockpit to settle the situation or were interrupted by flight attendants. In a quarter of those cases, pilots said they committed errors such as flying too fast or at the wrong altitude.