Surveillance data from the Germanwings Airbus A320 lost over south-eastern France appears to indicate that the flight climbed to 38,000ft briefly before descending.
The data, taken from automatic dependent surveillance transmissions, has not been officially verified. But it indicates that the aircraft reached the peak altitude over the Mediterranean Sea while operating the Barcelona-Dusseldorf route.
It also suggests the aircraft maintained this height for only a few minutes before starting to descend as it approached the French coast near Marseille.
Meteorological data for Marseille airport around the time indicates good visibility and no significant weather conditions.
German air navigation authority DFS says that there were 154 occupants on the aircraft including six crew members.
The aircraft crashed at 10:37 local time, it adds, about 50km north of Marseille.
There is no indication from the surveillance data of any attempt to divert from the course towards high terrain, despite the loss of altitude. There are several airports in the vicinity including Nice and Montpellier.
Unconfirmed reports suggest the airframe involved is D-AIPX, serial number 147, one of the oldest A320s in service. Flightglobal’s Ascend Fleets database shows this aircraft to be a 25-year old CFM International CFM56-powered example.
French civil aviation administration DGAC says the aircraft has come down near a town named Barcelonnette. The carrier is the low-cost arm of Lufthansa Group.