By Abhijith Ganapavaram and Arpan Chaturvedi

NEW DELHI, Oct 16 (Reuters) - The 91-year-old father of

the Air India pilot in a June crash that killed 260 has asked

India's Supreme Court to order an independent investigation that

takes into account causes other than pilot action, sources

familiar with the matter said.

The lawsuit represents a major escalation of protests by the

father and a pilots' union against the Indian government's

handling of the world's worst aviation disaster in a decade,

which came soon after takeoff in the western city of Ahmedabad.

The plea by the father, Pushkar Raj Sabharwal, for an

investigation by a panel of aviation experts headed by a retired

Supreme Court judge, comes weeks after he criticised the

government investigation.

He said two officials from India's Aircraft Accident

Investigation Bureau (AAIB) who visited him had implied that his

son, Sumeet Sabharwal, cut the fuel to the plane's engine after

take-off.

The government has denied such accusations, calling the

investigation "very clean" and "very thorough".

On October 11, the father told the court the investigation

team appeared to "predominantly focus on the deceased pilots ...

while failing to examine or eliminate other more plausible

technical and procedural causes," said one of the sources who

saw his filing.

It also asked for the government investigation to be closed

and handed to a new panel headed by a retired Supreme Court

judge that includes aviation experts, said the two sources, who

spoke on condition of anonymity.

The judges have yet to take up the case, which the Supreme

Court's website showed on Thursday had been filed jointly by the

father and the Federation of Indian Pilots against the

government, though it gave no details.

The AAIB, the civil aviation ministry, planemaker Boeing ( BA ) and

Air India did not immediately respond to Reuters requests for

comment. Sabharwal's father and the pilots' union did not

respond to emails seeking comment.

A preliminary AAIB report showed the Boeing

Dreamliner's fuel engine switches had almost simultaneously

flipped from run to cutoff just after takeoff.

The cockpit recording of dialogue between the two pilots

supported the view that Captain Sabharwal had cut the flow of

fuel to the engines, a source briefed on U.S. officials' early

assessment of evidence in July told Reuters.

The Federation of Indian Pilots has about 5,000 members.