Spy planes are conducting missions to track Russian movements, which might include listening to Russian soldiers’ phone calls home, according to one expert.
The planes are equipped with devices that allow them to collect signals sent from Russian bases and to intercept communications.
Sky News analysis of flight tracking data from a typical day in recent weeks shows that a host of NATO and Swedish planes are monitoring key Russian positions.
Scroll through the maps below to see what aircraft movements on 25 January – represented by yellow dots – can tell us:
What are the planes doing?
The aircraft are equipped with sensors that collect information on the electronic and radio signals being emitted in the areas they are monitoring.
Professor Mark Westwood, head of the centre of aeronautics at Cranfield University, said some of the aircraft typically “fly along a border and image off to the side, building up quite a detailed 3D picture of what’s operating there”.
Analysts stationed on the plane and back at base can then assess the information gathered and turn it into “intelligence” about Russian movements and capabilities.
The position of the planes also helps reveal where NATO countries are interested in and the position of Russian warships – a circling aircraft at sea suggests they are interested in something at the location.
A P-8 Poseidon in the centre – one of the RAF surveillance planes conducting missions. Pic: MOD
Why all the activity?
The flurry of reconnaissance flights over recent weeks has coincided with a Russian troop build-up on the Ukrainian border.
It is likely that the spy planes are feeding in more specific information about this build-up, such as the type of equipment the Russians are using.
But it is not just about equipment.
Some of the planes are capable of intercepting voice and text communications.
According to Douglas Barrie, a senior fellow for military aerospace at The International Institute for Strategic Studies, this includes “listening to chatter… and not just the official stuff. It could be troops phoning their boyfriend or girlfriend. It’s why there are protocols in place to not phone home, but people don’t always adhere to that. It’s human nature to want to ring home”.
An RAF camera operator aboard a surveillance aircraft. Pic: MOD
Are we seeing everything?
These flights are only recorded on flight tracking databases because their transponders are turned on. The military could turn them off if they wanted, so there may be more that are not being picked up.
However, given the amount of reconnaissance aircraft countries like the UK are known to have, Mr Barrie thinks we are probably seeing most, but not all, of the flights taking place.
And there is a reason for making this activity public. It sends a clear message that Russia is being watched.
But the activity will not all be one way. Russia, and many other countries, have reconnaissance planes of their own.
As Mr Barrie said: “Everyone’s listening to everyone else, on one level or another”.
Digital Production: Ganesh Rao
Additional flight tracking: Amelia Smith
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