Captain Ilpo Koskinen was piloting a FINNAIR DC-3 at an altitude of 3500 feet en route from Turku to Vaasa. It was evening and the weather was cavok. (Ceiling And Visibility O.K.)  The lights of another FINNAIR DC-3, travelling on the same course as Captain Koskinen from Turku to Pori, were visible ahead at an altitude of 2500 feet.

Over the radio, Captain Koskinen received a message from a military radar station at Pori that an unidentified target was approaching the aircraft head on at about 250 kts.  Although the radar station gave the radar position of the unkown target, and it passed between the two DC-3s, neither Captains of the aircraft could see the target which proceeded southbound on a steady course and vanished from the radar screen.

Below is a sketch showing the position of the two DC-3s and the path of the unidentified target.