Over the last year, NATO has tried to deter what it sees as Russian belligerence and to allay the fears of its allies by moving military forces—including fighter aircraft—further east. But this has brought NATO and Russian aircraft often into close proximity, especially over the Baltic, a region of airspace used by hundreds of flights each day, and made more complex because of the way air traffic management (ATM) is shared by the countries that border it.
EASA began investigating the issue late last year after a request from the European Commission on behalf of European Union (EU) member states that had reported foreign aircraft operating near their borders over the sea without transponders activated or filed flight plans. The countries were also unable to make radio contact with the aircraft, EASA says.
The problem came to international attention after Swedish authorities confirmed that in March last year a Scandinavian Airlines Boeing 737 carrying 132 passengers came within close proximity to a Russian reconnaissance aircraft, believed to be an Ilyushin Il-20 “Coot” over the Baltic Sea.
The European Leadership Network, a defense think tank, later classified that incident as high-risk, stating that it could have caused casualties and led to a direct military confrontation between Russia and Western states.

The number of intercepts prompted by Russian military aircraft in 
international airspace increased markedly during 2014. Here a Russian 
air force Ilyushin Il-20 “Coot” is escorted by a Royal Norwegian Air Force 
F-16 over the Norwegian Sea. Credit: Royal Norwegian Air Force

Although it does not name Russia as the source of these flights in its investigation of the activity, EASA’s report, published on April 15, says it has identified 15 additional instances in 2014, 13 of which were air-proximity incidents involving aircraft coming within 0.5 nm of one another horizontally or 300 ft. vertically. Three of the occurrences were airspace infringements.
EASA says 13 of the 16 incidents involved uncooperative military traffic. It recorded six more incidents in January and February of this year, compared with just six such incidents in 2013.
The agency says that calculating the number of non-cooperative military flights over the Baltic is a challenge because of the potential to count more than once flights that pass through different information regions. However, the data suggest the number of non-cooperative military flights over the Baltic has at least tripled since 2012, EASA says.
NATO fighters based in Lithuania and Estonia performed 150 interceptions during 2014, four times more than in 2013. These figures apply solely to the Baltic and do not include redirections of air traffic undertaken tactically by air traffic control (ATC) in other parts of Europe responding to uncooperative traffic in their airspace.
On several occasions, controllers working the airspace around the U.K. have been forced to divert traffic around the expected flightpaths of Russian Tu-95 Bear bombers flying over the North Sea or around Ireland into the U.K.’s southwestern approaches. NATO fighters escorted the Tu-95s during their probing missions.
At the same time, Russia accuses the NATO powers of flying intelligence-gathering missions in the Baltic with transponders switched off. According to recent statements from Russia’s mission to NATO, the alliance is flying as many as 8-12 missions in the immediate vicinity of Russia’s borders each week. The mission also characterizes the accusations of Russian military aircraft creating risks for civil aviation as part of a “tendentious information campaign.” 
“It is necessary to note that NATO states’ military aircraft always make their flights near Russian borders with transponders turned off,” Russian officials said in January. “However, it does not mean that they are invisible to airspace control means.”
Most recently, Russia has stated that a U.S. Air Force Boeing RC-135U Combat Sent it intercepted near the Kaliningrad Oblast had its transponder switched off. The U.S. State Department denied this and accused the Russian Su-27 pilot who intercepted the RC-135 of flying in an “unsafe and unprofessional manner.”
EASA says it would not be sensible to take dramatic measures, such as making the skies around the Baltic a no-fly zone for European civil airlines, as this would have “enormous economic consequences.”
But the presence of these military flights is considered highly hazardous to civil traffic because civil ATC authorities are often unaware of them. The situation could worsen, EASA notes, as forecasts suggest air traffic to the Baltic States could increase by 50% between now and 2035, adding greater risk if the geopolitical environment has not improved.
“It needs to be recognized that it is difficult to predict the evolution of the geopolitical situation and that this is beyond the control of civil aviation regulators,” the report states.
Currently, the airspace above the Baltic—at least above flight level 195 (19,500 ft.)—is classified as Class C airspace, which means that aircraft accessing it should file a flight plan, use two-way communications and have their transponders switched on, allowing civilian ATC to see them. But with non-cooperative military aircraft not following these rules, EASA says mitigating measures are needed to bring risk to an acceptable level.
The task is complicated, however, by the complex nature of the airspace around the Baltic, which is shared by several EU member states and has four functional airspace blocks.
The Baltic features a significant number of northern-to-southern traffic flows, as well as eastern-to-western ones, EASA says. These issues make the situation more complex, as traffic information about military aircraft cannot always be provided in a timely fashion to civil aircraft flying in the same narrow parts of the airspace.
EASA advises member states to follow the International Civil Aviation Organization’s recommendations in its Circular 330 document, which suggest enhanced cooperation or interoperability between the ATM systems used by military and civilian agencies. This includes making the primary surveillance data from military radars accessible to civilian ATC units, something presently done only in a handful of EU states.
“The Agency recommends that member states work closely together to further develop and harmonize concrete civil/military coordination procedures for ATM [at the EU] level,” the report states. It adds that the information should be disseminated when non-cooperative traffic is likely to be flying into different area control centers.
“Similar coordination has to be implemented at the tactical level between air defense and ATC units when scrambled aircraft become airborne for interceptions.”
The report states that primary surveillance radar detects only the rough horizontal location of a target but not necessarily its height. Passing this data on to surrounding aircraft as traffic information in their proximity would improve situational awareness for flight crews, EASA notes.
In several EU member states, permanent measures to reduce the risks are being discussed, the report states, including the technical feasibility for civilian ATC to view primary surveillance radar data. EASA says this data should be provided to civil ATC agencies to the “maximum possible extent.”