Exercise Trident Juncture took place in areas across Norway, Sweden and Finland.
While Norway is a full NATO member, Sweden and Finland are not.
Finland also shares a 1,340 km border with Russia, and it is believed that their decision to take part in Exercise Trident Junction could have angered Moscow.
It is claimed the Kremlin decided to carry out its own exercises nearby – and allegedly interrupted signals coming from satellites in the Arctic – affecting both military and civilian navigation systems.
Commercial airlines in Finland and Norway reported disturbances at the time, but the Kremlin denied any responsibility – calling the accusations a 'fantasty'.