“An Air Algerie flight en route to Algiers from Burkina Faso with 116 people aboard disappeared from radar early Thursday over the Sahara, the official Algerian news agency said.
Air navigation services lost track of AH0517 about 50 minutes after takeoff at 0155 GMT, the agency said. That means that it had been missing for hours before the news was made public.”
Yes, they kept it to themselves for several hours - I imagine them frantic to find out where the plane is.