What is known about the Air India crash and its investigation

NEW DELHI - Air Indias deadly plane crash that killed at least 270 people has triggered a wave of speculation about what led to the worlds worst aviation disaster in a decade, but authorities are slowly narrowing down areas of investigation.

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Heres what is known about the air crash so far:

VISUAL EVIDENCE

One of the strongest pieces of evidence that investigators are reviewing is a 59-second CCTV video clip that clearly shows the takeoff and the crash of the plane from Sardar Vallabhbhai Patel International Airport in Ahmedabad city, western Gujarat state.

The CCTV camera was located on the far left of the runway near a wall with barbed wire.

The video shows that the Tata Group-owned Air India plane takes off, gains some altitude, flies flat for a couple of seconds, and then starts descending with its tail down.

The descent of the plane starts roughly 17 seconds after takeoff. There is no fire visible around the engine or elsewhere when the plane appears to start going down, and has already crossed the airport boundary wall.

The landing gear visibly remains open throughout the clip.

It took roughly 33 seconds from wheels-up for the plane to crash, erupting into a huge fireball.

WHERE DID THE PLANE FALL

The plane crashed into the B.J. Medical College hostel.

Images of the dining area shortly after the incident showed wheels and other parts of the aircraft embedded in the walls, while debris and belongings of the students, including clothes and books, lay scattered on the floor.

Steel tumblers and plates still containing food lay on the few tables that were left intact.

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