French air accident investigators are briefing relatives of the people killed in last year's Germanwings crash on the results of their investigation.

Saturday's closed-doors briefings in Bonn and Barcelona come ahead of the release Sunday of French accident investigation agency BEA's final report.

Investigators have established that the co-pilot of Flight 9525 from Barcelona to Duesseldorf, Andreas Lubitz, deliberately crashed the plane into a French mountainside last March 24, killing 150 people. Lubitz had previously been treated for depression.

Christof Wellens, a lawyer for some victims' families, said they have questions about "how can such an ill pilot be in the cockpit, how is it possible that such an ill person gets a pilot license?"

He said "they have many questions and every answer is very necessary for the families."