Prosecutor said pair faced charges of unintentionally causing injuries and putting lives in danger, and establishing a campsite without permission.
Paris and Berlin announce plans to share air base and transport planes, probably at Orléans in central France, as part of a closer defence policy.
The Green activist, who was once known as 'Dany the Red', was expelled from France after leading student uprising in May 1968.
Poll says 72 percent hold favourable opinions of German chancellor, way above President Hollande's ratings which have sunk as low as 12 percent.
Head of German parliament's economics committee says Paris acted with 'ice-cold national industrial interest' in taking stake in French firm.
French president invites German chancellor to talks in Paris as both leaders pledge desire to continue 'their close cooperation' over Europe.
Ahead of German election, poll shows that Germany's chancellor enjoys higher ratings among French public than President François Hollande.
Social economy minister Benoit Hamon accuses Germany of seeking an unfair advantage over the rest of Europe by keeping pay artificially low.
Joachim Gauck will go to Oradour-sur-Glane where 642 people were massacred by Nazi soldiers in one of worst war-time atrocities in France.
The bus was carrying some 50 German teenagers to Spain when it ploughed into the back of a lorry on a motorway in south-central France.
French President Francois Hollande speaks about the continuing need for compromise between France and Germany.