The Bulgarian Air Force is the main type of armed forces for participation in joint and independent operations, both nationally and multinationally. They ensure air sovereignty of the Republic of Bulgaria by monitoring, securing and defending its airspace; they perform tasks on protection of critical infrastructure and strategic sites throughout the country. But the change of political system in the Republic of Bulgaria placed the Air Force in a position to undergo a serious test. The problems of transition deprived the Bulgarian Armed Forces, and in particular the Air Force from the opportunity to adequately modernize and preserve indispensable capabilities for national security. This paper argues that incompatibility between the Bulgarian Air Force and the forces of NATO partners exists, and it is a problem which has to be urgently solved.