A computer breakdown briefly disrupted all air traffic in France, but flights are now gradually resuming.
A spokesman for the civil aviation authority DGAC said the automatic flight plan system broke down Sunday morning and the reason is being investigated.
He said the problem had "no impact on flight security" and was fixed before midday.
The spokesman wasn't authorized to be publicly named according to the authority's rules.
However it temporarily halted all air traffic throughout French territory, and airports are still seeing residual delays.
That includes Paris' Charles de Gaulle airport, among Europe's busiest, where dozens of flights are running late.