The paper describes the preparation and performing of NATO Air Campaign against the Federal Republic of Yugoslavia in 1999, as a classic example of the conflict in which modern technological solutions changed the physiognomy of modern armed conflict. In the first chapter the way of NATO forces grow is described, as well as preparations which are performed by units of the Air Force and Air Defence of Yugoslav Army before the start of the armed conflict. The second chapter describes the most significant experiences and events that determinated the armed conflict between NATO and the Yugoslav Army, from the point of view of the use of the Yugoslav Air Defence Forces. Also, in the paper, the most important characteristics of the armed conflict, which resulted in a change in the physiognomy of modern armed conflicts, are abstracted. These characteristics are caused by the use of modern technological solutions in Air Force and Air Defence of warring parties. In the last chapter of the paper it is presented, a description of new, modern threats from airspace which were developed on the basis of the technological solutions of the weapons and equipment system in the last two decades. These threats, which primarily relate to the use of unmanned air vehicle, represent a new challenge for the Air Force and Air Defence of small countries in qualitative and quantitative terms (such as the Republic of Serbia), which requires their legal regulation, and also the construction of a technological solution that will be materialized response to this type of threat in the future.