Mystery still surrounds the crash of an Airbus A320 in the French Alps on Tuesday as aviation experts are left questioning why no distress call was made.

Two experienced pilots and an aviation engineer who spoke to this newspaper said that despite the aircraft’s sharp descent, the crew still had ample time to communicate any problems.

Lufthansa yesterday could not explain why the Airbus run by its low-cost Germanwings unit had crashed.

German Chancellor Angela Merkel, left, France's President Francois Hollande, centre, and Spain's Prime Minister Mariano Rajoy at the crash site. Photos: French Interior Ministry/Reuters

Investigators said the remoteness of the crash site meant it could be days before a clear picture of the tragedy emerged. However, they said the fact that debris was restricted to a small area indicated that the A320 was not likely to have exploded in mid-air, suggesting a terrorist attack was not to blame.

Lufthansa said the 24-year-old plane on Monday had repairs done to the hatch of the nose wheel bay. A spokeswoman said that was not a safety issue but repairs had been done to reduce noise.

Investigators looking into the crash yesterday extracted usable audio from the cockpit voice recorder recovered on the site. This will hopefully shed some light on what happened on flight 4U 9525 from Barcelona, Spain to Dusseldorf, Germany.

But France’s aviation security investigator, BEA, said it could be days before the sounds and voices heard could be analysed in detail.

French President Francois Hollande, German Chancellor Angela Merkel and Spanish Prime Minister Mariano Rajoy were in the Alpine region yesterday, ahead of an international tribute to the 150 victims.

The airliner was carrying 144 passengers and six crew. Most of the passengers were German, including 16 teenagers, and Spanish but there were also citizens of the UK, Australia and Belgium, among others.