In general, Germany has a south-to-north drop in altitude, from a maximum elevation of 9,718 feet (2,962 metres) in the Zugspitze of the Bavarian Alps to a few small areas slightly below sea level in the north near the coast.
Investigators were still unclear whether the plane's sudden drop in altitude was controlled or not, he added.
"There was no sudden drop in altitude or wild maneuver at any point of the flight," he said.
The French aviation regulatory authority (DGAC) said the aircraft did not issue a distress call, as initially reported, but that its sudden drop in altitude had led air traffic controllers to implement the "distress phase".
Then, reviewing global imaging system maps made with aerial photographs, he saw a dash of silver that looked like whitewater, where contour markings indicated a precipitous drop in altitude.
"He had no reason to turn [on] the button making the plane go down, he had no reason to prevent his captain to return to the cockpit, that's already a lot, he had no reason to refuse to reply to air traffic controllers that alerted him to his drop in altitude, he had no reason to refuse to tap a code to alert other aircraft in the zone … already that's a lot".
Aviation experts told French television that the steady drop in altitude suggested that the pilots had struggled to save the plane but eventually lost control.
I asked Nico and Katiushka if they knew about how in Vietnam the Americans would take suspected Vietcong up in helicopters and throw them out and then drop in altitude so they were cut to pieces by the helicopter's blades.
Tagged bees took off within 3 minutes of release, and initially often flew away with some drop in altitude (see supplementary Video S1).
The nose will want to drop, maintain altitude and attitude by pitching back on the controls.
