Pilots’ actions after the bird strike are an early focus of the investigation, according to people familiar with the probe.

South Korea released a preliminary report into last month’s deadly Jeju Air Co. crash that offers more detail on the role of bird strikes in the disaster, while still leaving crucial questions unanswered.

The feathers and blood stains on both engines of the Jeju Air plane were from the Baikal teal, a type of migratory duck that files in large flocks, according to a preliminary investigation report published on Monday.

Both engines of the Jeju Air plane that crashed last month contained duck remains, according to a preliminary report on Monday.

Jet engines are incredibly powerful, complex pieces of precision engineering, running at the finest of tolerances; bird strikes can push these tolerances to the limits. When a bird is ingested into an engine, the first thing the unfortunate creature will meet is the fan blades, typically rotating between 2200 rpm and 4500 rpm.

The investigation into the deadliest air disaster on the country’s soil remains ongoing, the report made available on Monday said, focused on the role of ‘bird strike’ and involving an analysis of the

South Korean authorities have submitted a preliminary report on last month's fatal Jeju Air crash to the International Civil Aviation Organization. The ongoing investigation focuses on a 'bird impact' as well as examining the aircraft's engines and landing systems.