Officials said the cause of the collision remains under investigation.
The crash happened about 3.30am local time on Tuesday off the coast of Oman while on a patrol.
Two teams faced intense security screenings while travelling to the World Cup.
It's the latest incursion of Russian drones into NATO airspace as Putin looks to expand his aggression from Ukraine into the Baltic States.
'People have been asking why this cold spot exists. We found the most likely answer.'
'For the first time, we have pinpointed the origin of these signals.'
