A European regulator found "issues" with Germany's aviation authority in a regular review of air safety enforcement, the European Commission said on Saturday.
Its statement did not say when the review was carried out, but the Wall Street Journal said the Commission told Berlin in November "to remedy the long-standing problems" - months before last week's Germanwings crash that killed all 150 people aboard.
The Journal cited two people familiar with the matter as saying EU officials had found the aviation authority, the Luftfahrtbundesamt (LBA), had a lack of staff, which could have limited its ability to carry out checks on planes and crew, such as medical checks.
"On the basis of EASA (European Aviation Safety Agency) recommendations, the Commission has addressed the issues to Germany to require compliance. Germany's replies are currently being assessed," the Commission spokesman said in the emailed statement.
The spokesman was not immediately available for further comment.
Parent company Lufthansa has said Lubitz told officials at an airline training school he had gone through a period of severe depression in the past, raising questions over whether medical checks of crew members by air-safety regulators and airlines are rigorous enough.
French air accident authority BEA has said its investigation into the Germanwings crash would study "systemic weaknesses" that might have led to the disaster, including psychological profiling.
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