A preliminary report into the crash of an Air India jetliner that killed 260 people in June is expected to be released by Friday, a step that could provide early details into the world's worst aviation disaster in a decade,

Aviation industry publication the Air Current first reported the focus on the fuel switches that help power the plane's two engines.

While the report from investigators could be made public on Friday, the three sources cautioned Reuters that plans could change and there was no clarity on how much information would be available in the document,