What is wake turbulence?

Phenomenon a focus of Flight 587 investigation

An image from a NASA video shows a test of the effects of wake turbulence.

(CNN) -- American Airlines Flight 587 took off on Monday morning and soared into clear, seemingly calm skies over New York, only to plummet to the ground in Queens minutes later -- felled, investigators say, perhaps in part by turbulence.

The National Transportation Safety Board says "wing tip vortices" from a Japan Airways Boeing 747 that took off minutes before the Airbus 300 might have contributed to, if not caused the loss of Flight 587's tail, its unusual trajectory and the subsequent crash.

Flight 587 was buffeted by two wakes of similar intensity and appeared to be flying normally before a significant force pushed the plane left, then left and right, according to preliminary readings from its flight data recorder. After that, "rudder position data became unreliable" and presumably the pilots lost control, according to NTSB director Marion Blakey.

Atmospheric and geographic conditions cause most cases of turbulence, as well as scores of bumps, bruises and more serious injuries. Wake turbulence is less well-known and, until now, has been less destructive -- especially with jumbo jets, which are thought to better handle such air disturbances than smaller, lighter jets.

VIDEO: Firefighters, residents respond Witnesses describe crash  MORE STORIES Final minute 'a very wild ride' Chat: Probing Flight 587 Sailor back from war killed in crash Fact Sheet  INTERACTIVE: Gallery 1 | Gallery 2 Flight 587's final seconds A300 tail assembly Crash site map Tracking the wakes  RESOURCES: Airline releases victim list

But there is at least one precedent: the 1994 crash of USAir Flight 427 near Pittsburgh, Pennsylvania, which killed 132 people. The NTSB believes wake turbulence was the initiating event in that crash, and subsequent tests showed turbulence from another jet can disrupt a trailing plane.

Planes create what John Wiley, owner of the flight school Aviation Safety Training, calls "a mini-horizontal tornado" in flight. An aircraft's wings stir up the tornadoes, known as vortices, as they slice through the air.

While the FAA recommends a four-mile separation between planes to avoid wake turbulence caused by such vortices, the unseen dangers can lurk and drift in the air for some time. In tests, engineers have measured vortices stretching 8 miles long, said CNN's Miles O'Brien.

And flights are more vulnerable at some moments than others -- when it flies at low-speed just after take-off and before landing, and when it banks while turning, as was the case for Flight 587.

"And remember, the pilot is not expecting an upset, especially at the lowest level climbing out and lowest level approaching a runway," Wiley told CNN.

That said, experts say planes fly through jet streams and "mini-tornadoes" all the time, without incident and often without even much discernible turbulence. Experts, like Wiley, say wake turbulence is likely a contributing, but not the lone factor in the crash of Flight 587, just as it was for USAir Flight 427.