REUTERS/Christophe Ena/Pool
German Chancellor Angela Merkel (L), French President Francois Hollande (C) and Spain's Prime Minister Mariano Rajoy pay respect to victims in front of the mountain in Seyne-les-Alpes, March 25, 2015, the day after the air crash of a Germanwings Airbus A320
In the latest development, a French senior military official who has knowledge of a cockpit audio recording says that one of the pilots was locked out of the cockpit and can be heard banging on the door minutes before the plane went down in a remote section of southern France.
As investigators continue to pick over clues from the crash site and examine two recovered black boxes, here's a timeline of everything we know about the events on the day of the plane crash, Tuesday, March 24.
Peter Macdiarmid/Getty Image Night falls on the alps near the area where a Germanwings flight crashed on March 25, 2015 in Seyne, France. 
9:30 a.m. - 9:31 a.m. GMT: Air traffic controllers are unable to make contact with the plane during these two minutes. A top government minister said on Tuesday that what happened during this time is key to the investigation.
9:45 a.m. GMT: The plane reaches its highest cruising altitude of 38,000 feet. Minutes later, the plane begins to descend rapidly without explanation.
9:47 a.m. GMT: An air traffic controller issues a "distress phase" due to the loss of radio contact and because the plane was losing altitude so quickly. Contrary to earlier reports, the plane itself did not issue a distress call, a spokesman for DGAC aviation authority said.
9:53 a.m. GMT: Contact between the airplane and French radar and French flight controllers is lost at an altitude of about 6,000 feet.
Francis Pellier MI DICOM/Ministere de l'Interieur/Getty Images
Rescue workers and gendarmerie continue their search operation near the site of the Germanwings plane crash near the French Alps on March 25, 2015.
9:53 a.m. - 10 a.m GMT: An official familiar with audio recordings from the German flight told the New York Times that one of the pilots was locked out of the cockpit in the minutes before the plane crashed. He can be heard knocking on the door and then trying to smash it down.
10 a.m. GMT: The plane crashes just before 10 a.m. GMT. In a news conference, the managing director of Germanwings says the plane crashed after dropping from an altitude of 36,000 feet to an altitude of 5,000 feet over a span of 8 minutes.
10:40 a.m. GMT: There are initial media reports of a plane crash in the French Alps.
11: 55 a.m. GMT: Investigators describe the horrific scene of the crash. "We saw an aircraft that had literally been ripped apart, the bodies are in a state of destruction, there is not one intact piece of wing or fuselage," Bruce Robin, prosecutor for the city of Marseille, told Reuters. French police confirm that no one survived. Later, the French Interior Minister says a black box from the crashed Germanwings plane has been found.
Currently, experts continue to examine the black box recorder found at the scene of the crash.
One of the pilots of the plane had 10 years of experience of flying for Lufthansa, German officials said at a press conference on Tuesday. Officials said the plane had been last checked by technicians on Monday and weather conditions were reportedly good at the time of the crash.