As South Korea mourns the devastating Jeju Air plane crash that killed all but two of the 181 souls on board on Sunday, experts have questioned some of the pilot’s actions in the fatal four minutes before it crashed at incredible speed.

The plane, a Boeing 737-800m belly-landed, skidded several meters down the runway and burst into flames as it hit an embankment at Muan International Airport on December 29 at 9am local time.

All 175 passengers and four crew members were killed, making it the deadliest air disaster on South Korean soil. Only two other crew members, a man and a woman, were rescued from the tail of the burning plane.

Investigators are still looking into whether a bird or bird strike caused the crash, a process expected to take several months to piece together the sequence of events.

But as the investigation continues, aviation experts have raised serious questions about nearly every element of the crash.

One wondered how there were so many mechanical failures in the landing gear and flaps, and how it was allowed to go so fast. Another wondered why the plane “turned around” and came in from the north.

A third questioned how airport officials allowed so many birds, as many as 200,000, to live in close proximity to the travel hub, increasing the risk of in-flight collisions.

“At this point there are many more questions than we have answers. Why was the plane going so fast? Why weren’t the flaps open? Why wasn’t the landing gear down?” said Gregory Aleghi, an aviation expert and former instructor at Italy’s Air Force Academy.