On night of 24 February 1995, I was on duty at the UNPROFOR radar console assigned by the Yugoslav authorities at Belgrade’s International Airport Area Control Centre (ACC). At about 02H00 in the morning, four large targets pumped-up flying over Bosnia, with a separation between radar contacts of about 10 Km (some 20 minutes between each target). The weather was rough, partly clouded with strong winds and reduced visibilities; not good for slow moving helicopters to contour mountain tops in order to avoid radar detection. The only option was to fly above the mountains on a straight line, but very slow, and expect the radar “Moving Target Indicator” filters would assume they were ground clutter and delete them out of the screen.
The initial radar contact was made over the Croatian Southern Krajina and the four large targets crossed the entire Bosnia airspace, eastbound, disappearing after crossing the border with the Serbian Republic of Yugoslavia. The radar blips were consistent and, due to its reduced speed, it took just over two hours between the initial and final radar contact. As the four targets got closer to the Yugoslav radar antennas, I could perfectly see that each large blip was in fact a formation of several other smaller blips.
In order to maintain a transparent and impartial posture, I called the Yugoslav air traffic supervisor and asked his comment. The Serbian supervisor looked carefully to the radar screen and said:
– “Those are migration birds!”
– “Migrations birds? Flying at the speed of an helicopter? During the winter? Going Eastbound? At 2 o’clock in the morning? With this lousy weather? I don’t think so! But okay, I will make sure to add your opinion on my report. We report what we see. The decision if it is or not a violation of the NFZ, is well about my pay grade.”
Although I knew that there were some species of birds that would fly at night on their migrations flights, and some of them flew fast, I was very much aware that birds fly south on autumn to avoid the winter conditions; not east, and not in the middle of the snowy Bosnian winter. Once again, NATO aircraft were in the air, but didn’t seem to react to those slow moving targets; because the AWACS radar filters deleted everything moving bellow 90Km/h (cars speed).
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