BOSTON -- Bit by bit, information has trickled out about the last moments of EgyptAir Flight 990 -- none of it helping investigators conclude what caused the jetliner to crash, killing all 217 people aboard.
As the National Transportation Safety Board and other experts go over radar data, debris and information from the plane's flight data and cockpit voice recorders, here is a summary of what is publicly known and unknown about the Oct. 31 crash:Question: What kind of plane was it?
Answer: The plane was a Boeing 767-300ER delivered to the airline in September 1989. The FAA said the plane had 33,354 flight hours.
Question: What do we know about the plane's final minutes?
Answer: The plane left Kennedy International Airport in New York for Cairo at 1:19 a.m. EST, rising to 33,000 feet and cruising normally. At 1:47 a.m., pilots made a final, routine radio communication with New York controllers.
Flight data recorder information shows the autopilot was disconnected. Eight seconds later, the plane began to dive nearly at the speed of sound, plunging 14,000 feet in just 36 seconds, which would have caused passengers to briefly experience weightlessness.
Both engines were actively shut off.
After the jet reaches 16,000 feet, it climbs to 24,000 feet, so fast it was subject to 21/2 times the force of gravity (the flight data recorder stops working during the ascent). The plane dives again, breaking apart at 10,000 feet and plunging into the ocean.
The last radar signal was at 1:52 a.m.
Question: What happened?
Answer: Authorities have not announced their conclusion. Aviation experts theorized that someone was in the cockpit trying to make the plane crash. Some suggest the roller-coaster maneuvers are evidence of a struggle for the controls, perhaps during a skyjacking or a suicide attempt.
Others have suggested a sudden decompression -- possibly caused by a door blowing off, or an explosion -- forced the pilot to rapidly descend to an altitude where passengers could breathe.
The FBI is examining criminal possibilities including terrorism, sabotage, skyjacking, suicide or some other issue with a passenger or a crew member. The NTSB suggested Monday that another agency like the FBI may take over the lead role in the investigation.
Question: What key questions do investigators want answered?
Answer: They want to know why the aircraft dove so sharply, whether the pilots were alone in the cockpit and why the engines and autopilot were shut off. They also want to know why an alarm went off in the middle of a dive. If there had been a mechanical problem triggering the dive -- for example, a fire, a loss of cabin pressure or the autopilot disconnecting -- the alarm would have gone off at the beginning of the dive, rather than in the middle of it.
Question: Why did the pilot shut off the engine while in the deep dive?
Answer: He may have been trying to make an emergency landing in the water, according to Chuck Eastlake, professor of aerospace engineering at Embry-Riddle Aeronautical University. Other experts have been at a loss to explain why a pilot would shut off both engines in flight.
Question: Why didn't the pilot notify air traffic control if there was an emergency on board?
Answer: One explanation may be that a pilot's responsibility is first to aviate, then to navigate and finally to communicate, said Ted Beneigh, associate professor of aeronautics at Embry-Riddle Aeronautical University. "If there was some kind of emergency, or some type of serious malfunction, you're going to be so busy, you're not going worry about communication," Beneigh said.
Question: What have the two recorders, or black boxes, revealed so far?
Answer: The flight data recorder ruled out several mechanical causes for the crash, including the possibility that the plane's initial plunge was caused by a problem with a thrust reverser and a total failure of the flight control system.
The NTSB said their first session listening to the cockpit voice recorder proved inconclusive, at least partly because the pilots were speaking Arabic.
Question: Are investigators likely to find a cause for the crash?
Answer: NTSB Chairman James Hall said he is confident they will. He said information from the plane's flight data and cockpit recorder bolstered his confidence of finding answers.