On December 28,  2014, AirAsia Flight QZ8501 crashed into the Java Sea, capping off one of the deadliest years in commercial air history.

Minutes before Air Traffic Control lost contact with Flight QZ8501, the pilot, Captain Iriyanto, requested permission to reroute around a storm. This request was initially denied by Air Traffic Control due to other aircrafts in the vicinity and the fact that the storm didn’t appear to be strong enough to warrant changing the plane’s route. However, when, shortly after their initial denial, Air Traffic Control contacted the plane giving permission for the pilot to reroute around the storm, the cockpit was unresponsive. After looking at black box data, investigators determined that the plane then made a sharp upward turn, resulting in a stall. Seconds later, the plane plummeted from the sky and disappeared from Air Traffic Control radars.

When investigators released this information to the media, the incident appeared to be the result of pilot error. However, in late January, two unnamed sources disclosed to Reuters that in the days following the crash, investigators had discovered there was a malfunction in QZ8501’s Flight Augmentation Computers (FAC) in the minutes prior to the crash. A plane’s FAC stabilizes it in turbulence and controls its rudder automatically. Without it, pilots must manually steer the plane and guide it through turbulence. For this reason, planes have two FAC computers.

It is believed that both FAC computers malfunctioned, forcing the pilot to restart them. In order to do this, the pilot had to leave his seat and go behind the co-pilot. During this period of time, the co-pilot was flying the plane through the storm manually with nothing adjusting the plane for turbulence.

It is assumed that at this point, the co-pilot over-adjusted for turbulence, forcing the plane into an upward trajectory. The plane’s rudder should have adjusted the course of the plane and prevented it from stalling. However, because the FAC was down, the rudder failed to prevent the plane from stalling.

After information about the FAC malfunction was released, another AirAsia pilot came forward. He reported that when he flew the same aircraft earlier in the week, there were glitches in the FAC. Investigators are now looking into how AirAsia addressed the issue and if they were endangering passengers by allowing the plane to fly.

The investigation also revealed that technically, Flight QZ8501 never should have been allowed to take off. A spokesman for the Indonesian Transportation Ministry admitted that Flight QZ8501 didn’t have the required permits for takeoff when it left Surabaya International Airport. Furthermore, while AirAsia had permission to fly from Surabaya to Singapore four days a week, it did not have permission to fly on Sundays, the day Flight QZ8501 disappeared. The Transportation Ministry is now launching an investigation into how a plane without the proper permits was cleared to fly.

Planes flying without proper permits result in more planes in the air than regulators allow. One result of this is planes fly much closer together. Flight QZ8501 was unable to reroute around the storm because there were other planes in the vicinity. However, if the proper number of planes had been in the sky, they should have been able to reroute around smaller storms if needed.

The issues that Flight QZ8501 faced highlight the growing pains of the Southeast Asian commercial air industry. As the Asian middle class grows, more and more individuals are beginning to fly. As a result, Southeast Asia is now full of new. rapidly expanding airlines which are trying to lower operating costs to undercut the competition and capture business. In the case of Flight QZ8501, this was evident in the airline’s flying more flights than it had permits for.

A more recent crash that highlights the impact of rapid expansion is that of TransAsia Flight 235, which crashed into a shallow river in Taipei on February 4, 2015. A viral dashcam video of the crash shows Flight 235’s wing hitting a freeway in Taipei as it falls from the sky. Black box recordings show that Flight 235’s right engine failed shortly after take-off. Flight 235 was also an ATR 72-600, which can fly with only one engine. It is believed the pilot of Flight 235 attempted to shut off the right engine, but instead, shut off the left engine, causing the plane to lose altitude and crash.

Pilot error is currently being investigated as a cause of the crash.