Ravi Thakur was delivering lunch tiffins to doctors at the hospital when a passenger aircraft took off from a nearby airport and, moments later, crashed into a dining facility where his mother, Sarla Ben Thakur, worked as a cook.

The crash and subsequent inferno killed her, along with Mr. Thakur’s daughter, Adhya. There had been a small swing for Adhya in the corner of the kitchen, where she could be watched while her parents were out delivering the food her grandmother cooked.

In the weeks since the June 12 crash in Ahmedabad, India’s worst aviation disaster in nearly three decades, Mr. Thakur’s time has been spent on seeking answers to how such a thing could happen: a plane falling from the sky, killing at least 260 people, including all but one of 242 onboard.

The preliminary investigation report released on Saturday — the day the family would have celebrated Adhya turning 2 — left families like Mr. Thakur’s unsatisfied.

The report said that fuel was switched off to both engines within seconds of takeoff, and that the airplane started losing thrust before it had even crossed the airport’s perimeter.

But it had no answers as to how the fuel was switched off, or why. The report included only a brief, confusing snippet of the conversation recorded in the cockpit between the pilots, where one asks whether the other moved the fuel switch, to which the second responds that he hadn’t.