Who caused the crash?

View from US

On 1 April 0915 (local time), the EP-3 plane was on a routine surveillance mission in international airspace over the South China Sea.

It was intercepted by two Chinese fighter aircraft. US Admiral Dennis Blair said such encounters were not unusual.

''They come up, take a look, report what they see and fly back. It's pretty routine,'' he said.

The collision occurred 113m (70 miles) off the Chinese island of Hainan.

''One of them bumped into the wing of the EP-3 aircraft,'' Admiral Blair said.

He said intercepts in recent months had become ''aggressive to the point we felt they were endangering the safety of Chinese and American aircraft''. The US lodged a protest with Chinese officials.

The admiral said the EP-3 is a big plane usually flying straight and level while fighter aircraft are more nimble.

''The faster, more manoeuvrable aircraft has the obligation to stay out of the way of the slower aircraft,'' Admiral Blair said. ''It is pretty obvious who bumped into whom.''

Apparently there was no communication between Chinese and American pilots.

There was sufficient damage to the American plane for the pilot to declare a mayday signal on an open international distress channel.

The White House said two of four propellers were damaged as well as the nose cone, wing flaps and equipment indicating the plane's air speed.

It said the plane plummeted 2,400m (8,000 feet) at one point.

The pilot diverted to an airfield on Hainan Island where the plane landed 15 to 20 minutes later. The US said it was standard procedure for a damaged plane to land at the nearest airport after issuing a mayday call.

The last communication from the plane was that it had landed safely and all 24 military personnel on board were uninjured.

US Senator Richard Lugar, who sits on the Senate Intelligence Committee, has said that the Chinese pilot who is believed to have died, Wnag Wei, had challenged the US plane before, but this time had "exceeded his grasp".

US surveillance crews are said to become quite familiar with Chinese pilots who intercept them and often photograph them.

View from China

After detecting a US plane conducting surveillance off the city of Sanya, two Chinese F-8 fighter jets took off and carried out ''routine tracking'' of the aircraft.

At 0907 the all the planes were flying in the same direction, 400m apart with the US plane on the right.

A Defence Ministry spokesman said ''the immediate cause of the collision was the violation of flight rules by the US plane which made a sudden and big movement to veer towards the Chinese plane,'' the state news agency reported.

''The US plane's nose and left wing rammed the tail of one of the Chinese planes causing it to lose control and plunge into the sea,'' he said.

The pilot parachuted from his plane and is still missing, while the other pilot landed his F-8 safely.

At 0933 the US plane illegally entered Chinese territorial airspace and landed at Lingshui Airport in Hainan, the spokesman said.

The analysts

Nobody really knows how or why the mid-air collision happened.

Many Western analysts, including the specialist publication Jane's Defence, argue that the two Chinese F8 fighters were dispatched to intercept the US surveillance plane and "hemmed in" the much bigger plane, in an attempt to make it change course.

The slightest misjudgement by either the US or Chinese pilot could have caused the collision.

They generally argue that the US plane was unlikely to veer suddenly to the left, as claimed by Beijing. It is a big and cumbersome plane that the far more nimble Chinese jets should have been able to avoid.

The Washington Post newspaper has reported that US officials are saying the Chinese interceptor plane that crashed was actually flying under the US plane. The collision occurred, according to this report, after the US surveillance plane started banking.

One report says that Wang Wei was killed instantly after the collision. The report claims that he ejected into one of the propellers of the US surveillance plane.