An association of Indian pilots has defended the crew of the Air India Flight 171 which crashed in June, killing 260 people.

The Indian Commercial Pilots' Association (ICPA) said the crew "acted in line with their training and responsibilities under challenging conditions and the pilots shouldn't be vilified based on conjecture".

"To casually suggest pilot suicide without verified evidence is a gross violation of ethical reporting and a disservice to the dignity of the profession," it added.

A preliminary report did not blame the pilots. It said seconds after take-off, both of the Boeing 787 Dreamliner's fuel-control switches moved to the "cut-off" position, starving the engines of fuel.

The report released on Saturday gave details of the cockpit voice recording with one pilot asking the other why he "did the cut-off", to which the other replies that he didn't. The recording doesn't clarify who said what. Data shows the switches were then moved to "run" position, but the plane crashed within seconds.

Aviation experts and pilots say the fuel switches are designed to prevent accidental activation and they must be pulled up to unlock before flipping. Protective guard brackets further shield them from accidental bumps.

The preliminary report does not throw any light on how the switches were moved to cut-off, but since its release, sections of media and social media has been awash with unsavoury speculation about the role of pilots.

"We are deeply disturbed by speculative narratives emerging in sections of the media and public discourse - particularly the reckless and unfounded insinuation of pilot suicide," the Indian Commercial Pilots' Association (ICPA) said in a statement released late on Saturday night.

"Let us be unequivocally clear: there is absolutely no basis for such a claim at this stage, and invoking such a serious allegation based on incomplete or preliminary information is not only irresponsible - it is deeply insensitive to the individuals and families involved."

The statement added that until the official investigation was concluded and the final report was published, "any speculation - especially of such a grave nature - is unacceptable and must be condemned".

The preliminary investigation was led by Indian government with experts from Boeing, General Electric, Air India, Indian regulators and participants from the US and UK. A final report is due to come out in a year.

On Saturday, another pilots' grouping - the Airline Pilots' Association of India (ALPA India) - had raised concerns over the way the investigation was being handled.

It highlighted that the report also mentions that in December 2018, the US Federal Aviation Administration issued a Special Airworthiness Information Bulletin (SAIB) highlighting that some Boeing 737 fuel control switches were installed with the locking feature disengaged.

While the issue was noted, it wasn't deemed an unsafe condition requiring an Airworthiness Directive (AD) - a legally enforceable regulation to correct unsafe conditions in a product.

The same switch design is used in Boeing 787-8 aircraft, including Air India's VT-ANB which crashed. As the SAIB was advisory, Air India did not perform the recommended inspections.

Taking note of the bulletin, ALPA India said "it demands clarity on whether the recommendations outlined in the bulletin were implemented before the flight". (Air India hasn't commented on the specific issue.)

The pilots' union said it was "surprised at the secrecy surrounding these investigations" and alleged that "suitably qualified personnel were not taken on board for the probe".

"We feel that the investigation is being driven in a direction presuming the guilt of pilots and we strongly object to this line of thought," ALPA India's president Captain Sam Thomas said in the statement.

The union also urged the authorities to allow it to join the process "even in the capacity of observers so as to provide the requisite transparency in the investigations".

Following the report's release on Saturday, Indian Civil Aviation Minister Ram Mohan Naidu told reporters to not "jump to any conclusions at this stage. Let us wait for the final report".

Describing the pilots and crew in India as the "backbone of this civil aviation", he said India had "the most wonderful workforce in terms of pilots and the crew in the whole world".

Flight 171 had taken off from the western Indian city of Ahmedabad for Gatwick in London on 12 June with 242 people on board. The crash killed 241 onboard - one passenger miraculously survived - and 19 people on the ground.

The report says the pilots, based in Mumbai, had arrived in Ahmedabad the previous day and were adequately-rested. They had passed breathalyser tests and were cleared to fly, it adds.