Aviation long beset by turbulence

— -- A pocket of apparent turbulence Monday that injured more than two dozen people aboard a Continental Airlines jet over the Atlantic Ocean exemplifies a safety problem that has plagued aviation for decades, according to pilots, weather experts and federal data.

Bumpy air is the biggest cause of airborne injuries outside of fatal crashes, according to the Federal Aviation Administration. While other causes of aviation accidents have steadily declined, incidents of turbulence causing serious injury have remained flat for decades.

The Boeing 767, flying from Rio de Janeiro to Houston, struck turbulence about 4:30 a.m. while flying north of the Dominican Republic, Continental and the FAA said.

Four people suffered serious injuries out of the 14 who were taken to hospitals after the jet made an emergency landing in Miami, said Miami-Dade Fire Rescue spokesman Elkin Sierra. The airline said at least 28 people were treated at the airport.

About eight serious turbulence accidents have occurred each year since 1990, according to National Transportation Safety Board data. Two people have died during that time, and about 10 people a year suffer severe injuries such as broken bones. "It is a stubborn problem. It remains a persistent concern," says Linda Orlady, vice chairwoman of the Air Line Pilots Association's safety committee.

Pilots do not have equipment that will reliably warn them when they approach turbulence, Orlady said. Warnings passed from air-traffic controllers and airline dispatchers are not always timely or reliable, she said.

The FAA and the aviation industry studied the problem and reported in 2004 that it costs airlines $28.5 million a year. The report suggested greater emphasis be put on requiring passengers to stay seated and buckled in during flights.

Turbulence is caused by pockets of rough air that are equivalent to roiling white water in a river. Some turbulence is associated with storms, which can be avoided by pilots — but "clear-air turbulence" can hit without warning.