Germanwings A320 crash: Safety experts speculate cause of flight 4U9525 downing

The Airbus A320 is the workhorse of Europe's aerospace industry, transporting more than a million people a day from business travellers to backpackers. The 150-seat medium-haul jet is one of the world's most intensively used together with its main rival, the Boeing 737.

The Germanwings aircraft that crashed in the French Alps, killing all 150 people on board, was also flying on the industry's most widely sold engines, made by French-US venture CFM.

While it is still too early to determine what caused the crash, safety and aviation experts agree that the A320 safety records are among the industry's highest.

"In the last 15 years the Airbus 320 has had 12 accidents. Now, two of them are under investigation, the one that happened today [24 March] and the one that happened in Indonesia in December of 2014. That leaves us 10. Of the 10 eight were human errors," said Michael Barr, an expert in aviation safety and senior instructor at the University of Southern California.

"The majority of accidents on the Airbus 320 are human errors, training of the crews," said Barr.

The A320 made dramatic headlines in 2009 when a US Airways jet ditched safely in the Hudson River after a bird strike and again in December 2014 when an Indonesia AirAsia A320 plummeted into the Java Sea, killing all 162 people on board.

More than 3,600 of the jets are in operation and another 3,700 are waiting to be built as Asia's economic expansion fuels record demand.

Put together with the rest of the A320 family of twin-engine, single-aisle jets – the A318, A319 and A321 – more than 6,000 are in use several times a day, whether feeding passengers into hubs for traditional carriers or fuelling the growth of low-cost airlines.

To ordinary passengers, the A320 looks much like other jets. But in the cockpit it represented a revolution when it began service in 1988 as the first "fly-by-wire" jetliner relying on computers to fly within safe limits and replacing the usual control yoke with a side-stick, inspired by the F-16 fighter.

The increased reliance on computers, though increasingly common across the industry, prompted a bitter debate between Airbus and pilot unions over whether too much control was being taken out of human hands. The argument rumbles on to this day.

Barr said: "The current pilots basically fly digital airplanes, and the digital airplane is like your computer, as long as you hit the right buttons in the computer you're going to get the right answer but if you hit the wrong button and a screen comes up and you don't know where that screen came from, now what do you do?

"Now you're looking around trying to figure out what's going on inside that computer. Before the computers came pilots were trained to understand the airplane itself. You became part of the airplane. I always like to put it this way, previous airplanes, you were in charge. You were the pilot. Current airplanes, sometimes you become the passenger and the airplane flies you. You don't fly the airplane."

To airlines, the main value of the $97m (£65m) jet is reliability and quick turnarounds, features it shares with the rival 737.

Boeing statistics for its rival's best-selling model show that up to end-2013, there were 0.14 fatal A320 accidents per million departures where the plane was destroyed or written off.

The comparable versions of Boeing 737 had a rate of 0.11 per million departures, making them both among the industry's safest models compared with the industry average of 0.76, or more than 4.6 for the earliest days of the jet age.

"I have looked at the Airbus 320 for many many years and it's just an excellent airplane but an airplane is only as good as their operators," said Barr.

Safety experts noted that accidents during the cruise phase of the flight are rare, even though this comes less than three months after the AirAsia disaster.

According to separate surveys published last year by manufacturers Airbus and Boeing, only 10 to 12% of fatal accidents take place when the aircraft is at cruise height.

One of the plane's black box records has been found at the crash site, about 65 miles north of the Riviera city of Nice and will be examined immediately.