411A
The aircraft did not land at Nice. Obviously if it had done so the passengers would have got off, but at least they were in their desired country of destination. As far as I am aware it was a re-flightplanning excercise. When overhead Nice they had sufficient fuel with reserves to continue to Paris. We used to do this flying northbound from Africa in the 60's, and is perfectly legal so long as you have the required trip, alternate and reserves when overhead the en-route alternate. The procedure is covered on most MCC courses.
Airclues