Much is still unknown about what caused an Air India flight on June 12 to crash, killing at least 260 people. The London-bound plane crashed shortly after taking off from an airport in the city of Ahmedabad and ripped through the dining hall of a nearby medical college.

It was India’s worst aviation disaster in decades: All but one of the 242 people onboard were killed, as were many others on the ground.

It may take investigators many months to reach conclusive answers. But a preliminary report released on Saturday by India’s Aircraft Accident Investigation Bureau offered the most detailed account yet of the crash.

Here’s a timeline, according to the report.

11:17 a.m. local time: The plane, a Boeing 787-8 operated by Air India, touches down at the Sardar Vallabhbhai Patel International Airport in Ahmedabad after its previous flight, a domestic hop from New Delhi.

The crew of the previous flight reported a defect, which seemed related to a sensor measuring a stabilizer on the plane.

11:55 a.m.: The crew for Air India flight 171 — two pilots and 10 cabin crew members — arrive at the airport. They are given routine preflight breath analyzer tests, which are typically given for alcohol, and pass.