One of the first photos of the scene showed a helicopter circling above the mountainside with many small pieces of debris.

Flight 4U 9525 of German low-cost airline Germanwings crashed yesterday while on the journey from Barcelona, Spain, to Duesseldorf, Germany.

Technical error

The chart shows 4U 9525’s sudden descent (blue line).

Technical errors are the second most common cause of plane crashes, accounting for one-fifth of all aviation accidents that have occurred from the 1950s to the present.

Plane Crash Info site built the above database based on information from more than 1,000 fatal commercial aircraft crashes with more than 18 people on board.

Some sources said that the German plane suddenly lowered altitude before falling, from 11.58 km to 7.32 km, in less than 6 minutes.

In addition, a witness present near the scene said the plane made very strange sounds, lasting about 8 seconds, before the crash.

France 24 TV channel also said that technical errors were most likely the cause of the disaster.

The flight crew lost consciousness

Some plane crashes stem from the pilot having health problems or losing consciousness if the cockpit suddenly depressurizes or is affected by the smoke of a fire.

According to a notice from the French civil aviation agency, the flight crew did not send an emergency signal.

However, according to aviation analyst Mary Schiavo, the fact that the plane descended 4.26 km within 6 minutes showed that the plane did not stall and the pilot still controlled the plane to some extent.

Ms. Schiavo explained that the decrease in altitude meant that the pilot wanted to make an emergency landing or that the plane was gliding under his control.

Terrorist kidnapping

Final position of the Airbus A320.

Reporter Virginie Herz from France 24 said that the cause of the plane’s terrorist attack could not be ruled out.

According to statistics, causes stemming from external sabotage account for less than one-tenth of aircraft accidents.

Spain has also suffered terrorist attacks before when an al-Qaeda member bombed a subway train in Madrid in 2004, killing 191 people.

But experts are also reconsidering the hypothesis that there was a bomb on the plane because if that were true, the pilot would have to send a distress signal to air traffic control.

Weather

Bad weather conditions have been eliminated by many people from the list of causes that caused the plane to crash because when the plane crashed in the Alps there were no signs of a storm.

`Many provinces in France are struggling with bad weather, but the Alps region is the opposite,` wrote French weather website La Chaine Meteo.

Dr. Paul Williams, an atmospheric scientist at the University of Reading, England, also said that weather was not the reason the plane crashed.

Pilot error

Pilot error is one of the most common causes of plane crashes, accounting for 53% of plane crashes, according to data provided by the website Plane Crash Info.

It’s still too early to confirm human error caused the accident, but it will be a possibility experts will consider.