- 10:30 a.m. ET: Air traffic controllers set out a distress signal after controllers became concerned at the loss of radio contact with the doomed Germanwings plane and the speed of the plane's descent, a spokesperson for the French civil aviation authority said.
The crew of the plane itself did not issue a distress call before crashing in southern France, the spokesperson said.
- 10:20 a.m. ET: Those on Tuesday's fallen Germanwings plane include 67 German citizens, but "this figure may change" when the passenger list is checked with relatives, according to airline executive Thomas Winkelmann.
- 10:11 a.m.: The fallen aircraft last had contact with French radar services at 10:53 a.m., according to the Germanwings executive.
He called Tuesday a "tragic, very sad day for Germanwings and also the whole Lufthansa family."
Two babies were among those on board, according to Winkelmann.
The captain of the downed plane flew for Germanwings for more than 10 years, and had more than 6,000 flight hours on this model of Airbus.
- 9:46 a.m.: German Chancellor Angela Merkel said Tuesday that "we don't know much about the flight and the crash yet. And we don't know the cause."
- 9:46 a.m.: Merkel -- who plans to go to France on Wednesday -- said that she's been in touch with France's President and Spain's Prime Minister, with all agreeing to "help each other in any form."
"Many Germans" are among the mourners, added Merkel, expressing condolences to all those who lost loved ones in the crash.
"We have to think of the victims and their families and their friends," she said.
A Germanwings Airbus A320 plane crashed Tuesday in the foothills of the Alps in southeastern France, French Prime Minister Manuel Valls told reporters.
Valls said he fears those aboard the flight from Barcelona, Spain, to Dusseldorf, Germany -- 142 passengers and six crew members -- may be dead. A short time later, Germanwings executives said that there were at least 150 people aboard, 144 of whom were passengers.
French President Francois Hollande also said no survivors were expected. The plane crashed near Digne-les-Bains, in the Alpes de Haute Provence region, Valls said.
"The conditions of the accident are not yet clear but lead us to believe there will be no survivors," Hollande said.
Spanish King Felipe VI said there was a "high number of Spaniards, Germans and Turks" on the doomed Germanwings flight.
Mariano Rajoy, Spain's Prime Minister, tweeted that he will return to Madrid, put together a "crisis team" and send a minister to France.
German Foreign Minister Frank-Walter Steinmeier said the German government had already set up a crisis center in response to the "terrible news" and was in close contact with the French authorities.
"In these difficult hours, our thoughts are with those who have to fear that their close ones are among the passengers and crew," he said.
Hollande warned that it could take some hours for the emergency services to reach the remote crash site.
The crash happened in mountainous terrain near the Prads-Haute-Bleone community, French police Capt. Benoit Zeisser said.
Because of the terrain, it will be a difficult site for rescuers to access, Zeisser said. A police helicopter is in the area, he said.
The sports hall of a local school for students aged 11 to 14 has been freed up to take in bodies of the victims of the plane crash, Sandrine Julien from the town hall of Seyne-les-Alpes village told CNN.
The school remains open, she said. Seyne-les-Alpes is about 10 kilometers (6 miles) from the crash site on a straight line.
Mountain guide Yvan Theaudin told BFMTV the crash was in the area of the Massif des Trois Eveches, where there are peaks of nearly 3,000 meters (1.9 miles). It's very snowy in the area and the weather is worsening, he said, which could complicate search and rescue efforts.
Responders may have to use skis to reach the crash site on the ground, he said.
A distress call associated with plane was sent at 10:45 a.m. local time (5:45 a.m. ET), French Interior Ministry spokesman Pierre-Henry Brandet told CNN affiliate BFMTV.
Germanwings Flight 9525 had left Barcelona airport at 10:01 a.m., the airport website said.
Lufthansa: We hope to find survivors
Germanwings is a low-cost airline owned by the Lufthansa Group. Lufthansa has gradually been transferring many of its short-haul flights to Germanwings, with the exception of flights operated from its Frankfurt and Munich hubs.
Lufthansa said Tuesday on Twitter that "we do not yet know what has happened to flight 4U 9525."
"If our fears are confirmed, this is a dark day for Lufthansa. We hope to find survivors," Lufthansa said on Twitter.
Founded in 2002, Germanwings became a wholly owned Lufthansa subsidiary in 2009.
The twin-engine Airbus A320s, which entered service in 1988, is generally considered among the most reliable aircraft, aviation analyst David Soucie said.
The crash site is closer to Barcelona than Dusseldorf, but well into the flight. Crashes midflight are rare, as most happen near takeoff or landing, CNN aviation analyst Mary Schiavo said.
According to the U.S. Federal Aviation Administration, just under 16% of aviation accidents occur during the cruise portion -- meaning after the climb and before descent -- of a flight. Accidents are more common during takeoff and landing.
Plane dropped 14,000 feet in six minutes, online flight tracker shows
It is too early to know what happened, but Schiavo said there were some clues that rescuers and investigators will look at.
First is the speed of the jet's descent.
According to an online flight tracker that records altitude, the plane was at 38,000 feet, and six minutes later had dropped to 24,000 feet -- a drop of 14,000 feet.
This could indicate that there was not a stall, but that the pilot was still controlling the plane to some extent, Schiavo said.
Had there been an engine stall, the plane would have crashed in a matter of minutes, she said.
That small piece of information about the descent means that the pilot could have been trying to make an emergency landing, or that the plane was gliding with the pilot's guidance, Schiavo said.
A scenario where the plane was gliding is potentially more dangerous because wide fields for landing would be hard to come by in the mountains, she said.
Mayor: Area of crash site is sparsely populated
The mayor of the French community of Barcelonnette, near the crash site, told CNN affiliate BFMTV that emergency responders had been sent to the crash area. A helicopter has also been deployed to try to locate the precise crash site, he said.
The valley is long and snow-covered, and access is difficult, Barcelonnette Mayor Pierre Martin-Charpenel said. It was well populated in the 19th century but there are almost no people living there now, he said.
It's an out-of-the-way place with magnificent scenery, he said.