The head of the Danish pilots association, Lars Bjørling, has urged politicians to act quickly to ensure there isn't another incident like the one in which an SAS flight came within seconds of colliding with a Russian military plane earlier this year.

Bjørling wants the nations in the Baltic to agree that military planes should fly with their transponders on so that they are not invisible to civilian airlines.

”This is very serious. There are military aircraft flying around international airspace without a flight plan and transponder so they can only be seen via primary radar,” Bjørling told Ingeniøren newspaper.

“That’s a really bad idea and I don’t understand why they do it.”

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A close call
In March, an SAS airliner came within 90 metres of a Russian Iljushin Il-20 m surveillance aircraft because the military plane was flying without an engaged transponder, which reveals aircraft to pilots and air traffic controllers alike.

The Swedish defence saw the Russian aircraft on its primary radar and managed to warn the SAS plane so it could avoid disaster, but Bjørling said that this method has its limitations because primary radar is not adequately accurate in ensuring elevation separation between aircraft.

There can be a 1,000 foot uncertainty, which is the generally accepted distance limit for how close aircraft can safely come into proximity of one another.

There are no publicly accessible figures on how often civilian and military aircraft meet one another in the air, but SAS said that it had experienced more encounters than usual as of late.