A Japan Airlines flight was cleared for takeoff about two minutes and 20 seconds before the American Airlines flight, but it actually took off one minute and 45 seconds ahead of Flight 587, National Transportation Safety Board Chairman Marion Blakey said Wednesday.

Federal Aviation Administration regulations require four nautical miles, or two minutes, of separation between departing flights.

Officials described the the JAL 747-400 as one of the biggest aircraft made, weighing 800,000 pounds. Being so large, officials said, the plane may take longer on the runway and would create a more intense wake turbulence.

Blakey said preliminary analysis of the flight paths of both planes showed that the JAL flight was about four nautical miles out from the American Airlines flight and traveling 800 feet higher. Wind conditions at the time of Flight 587's takeoff, she said, were "consistent with a wake vortex encounter" -- a phenomenon some experts characterize as a "horizontal tornado" that can cause an aircraft to go out of control.

The American pilot was heard commenting on wake turbulence about 30 seconds before the cockpit voice recorder shut down.

An FAA incident report shows the same plane that crashed Monday experienced severe turbulence over the Caribbean island of Martinique in 1994 when 46 passengers and flight attendants were injured.

NTSB board member George Black Jr. said the Airbus A300's maintenance records are being reviewed as part of the investigation. Preliminary reports, he said, indicate there were no delayed maintenance items noted in the log.

The jet took off for Santo Domingo, Dominican Republic, from John F. Kennedy International Airport shortly after 9 a.m. EST Monday but remained aloft less than three minutes. It crashed into a residential neighborhood in the Rockaway section of the New York City borough of Queens, killing all 260 people on board. In addition, five people from the neighborhood were killed in the fiery impact.

Black said investigators are wading through "a good wealth of data" contained on the flight data recorder after the manufacturer was able to fix a damaged memory module. That data should indicate how much force the turbulence put on the aircraft, how the pilot reacted and when the rudder separated from the aircraft, former NTSB Vice Chairman Bob Francis told CNN.

Black said the recorder contains 81 hours of data that continues past the point where pilots lost control of the plane "but ends before impact."

The plane's tail section and both engines separated from the body of the jet before it hit the ground. Whether the plane's tail section sheared off before both engines detached could be a significant clue, investigators said.

"The pieces of the tail were first in the debris trail, which generally indicates they came off very early," Black said.

The tail, pulled virtually intact from the waters of Jamaica Bay half a mile short of the main crash site Tuesday, showed no obvious signs of an explosion. The aircraft's rudder fell closer to the crash site.

Black said the fittings that hold the tail fin onto the fuselage was last inspected in December 1999. He noted that prior to the plane's delivery to American Airlines in 1988, the left center fitting was found to be faulty, and the manufacturer repaired and reinforced it.

One of the engines landed in a gas station parking lot and the other crushed a boat parked in a residential driveway

Black said the engines will be taken to Tulsa, Oklahoma, where they will be taken apart and examined.

The cockpit voice recorder revealed a rattling noise from the jet's airframe less than two minutes into the flight, followed by a report of turbulence. A second rattle was followed seconds later by a call from the co-pilot, who was at the controls, for maximum power. The cockpit conversation then suggested loss of control of the aircraft -- and the recording ended at two minutes, 24 seconds.

Black said a spectral analysis of the cockpit voice recorder revealed that the engines can be heard running as the pilots talk about losing control of the plane -- a clue that could help investigators determine the sequence of the aircraft's breakup.

More information may come from interviews with the pilot of a business plane who was heard by ground control describing the incident as it happened. Black also said the plane may have been caught by a government surveillance camera.

The known dead included 251 passengers, five of them infants, and nine crew members. Most of those aboard the plane were Dominicans heading home or to visit relatives

At least 11 houses were damaged in Monday's crash, including four that were destroyed and four others seriously damaged. The tragedy further battered a community that was dealing with the deaths of more than 60 residents in the September 11 terrorist attacks on the World Trade Center.

Investigators said they had no evidence indicating the crash was "anything but an accident" but also said they could not rule out sabotage.