Rescue teams have returned to Germanwings flight 4U 9525 crash site in the southern French Alps for search and recovery operations.
The Airbus A320 crashed on March 24 with 150 people on board.
Officials warn the operation could last for days in a remote mountain ravine between Digne and Barcelonnette.
The leaders of Germany, France and Spain are due to visit the crash site.
Germanwings flight 4U 9525 from Barcelona to Duesseldorf crashed after an 8-minute rapid descent, officials say. There were no survivors.
Officials believe 67 of the 144 passengers were German citizens, including 16 high school students returning from an exchange trip.
A day of mourning was being held at the Joseph-Koenig-Gymnasium school in Haltern-am-See, north-west Germany, where the students were from.
More than 40 passengers were believed to be Spanish and the flight was also carrying citizens of Australia, Japan, Colombia, Turkey, Denmark, the Netherlands, Belgium and the UK.
The plane’s cockpit voice recorder – recovered by a helicopter team on Tuesday – was damaged but could still provide information, French Interior Minister Bernard Cazeneuve said.
Finding the second “black box” – the flight data recorder – will be a key aim of Wednesday’s search operation.
A team of police officers spent the night on the mountain, securing the site.
French President Francois Hollande, German Chancellor Angela Merkel and Spanish PM Mariano Rajoy are expected to visit the crash scene later.
Mariano Rajoy has already declared three days of national mourning in Spain.
Bereaved relatives are also expected to visit the scene on March 25. The mayor of Seyne-les-Alpes, the town nearest the crash site, said local families were offering to host them.
Footage shot from a helicopter on March 24 showed plane parts scattered on the rocky mountainside.
“The site is a picture of horror,” German Foreign Minister Frank-Walter Steinmeier said after being flown over the ravine.
“Everything is pulverized. The largest pieces of debris are the size of a small car,” Gilbert Sauvan, president of the general council Alpes-de-Haute-Provence, told the Associated Press.
Germanwings, a low-cost airline owned by Germany’s main carrier Lufthansa, said some crew members were unfit for service on March 25 “due to emotional distress”.
The airline said one flight was being cancelled but remaining flights would be according to schedule.
Lufthansa and Germanwings staff held a minute’s silence on Wednesday morning.
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