German prosecutors said the co-pilot suspected of deliberately crashing a Germanwings airliner into the French Alps hid details of an illness.
The man suspected of deliberately crashing a Germanwings A320 plane in the French Alps required treatment for depression, German media say.
Regular assessments were recommended in Andreas Lubitz's official notes after a serious episode some years ago.
The Barcelona-Duesseldorf plane crashed on Tuesday, killing 150 people.
Data from the plane's voice recorder suggest Mr Lubitz purposely started a descent as the pilot was locked out of the cockpit.
Several airlines have now pledged to change their rules to ensure at least two crew members are present in the cockpit at all times.
Police have searched two German properties used by Mr Lubitz, taking away boxes and a computer.
When Mr Lubitz finished training in 2009, he was diagnosed with a serious depressive episode and went on to receive treatment for a year and a half, the German news site Bild reports.
Internal documents quoted by Bild and German broadcaster ARD say a note on Mr Lubitz's aviation authority file recommended regular psychological assessment.