This Note identifies major trends since 1950 in the evolution of the force structures of non-U.S. allied air forces in NATO's Central Region. It also examines the direction of these trends to the year 2005, assuming no arms control. The number of squadrons in NATO's Central Region airpower has remained remarkably stable since the mid-1960s, as has the contribution of each nation. These nations have steadily increased the number of multirole and all-weather squadrons. Aircraft designed by multinational consortiums account for a growing percentage of NATO's aircraft; conversely, the share of aircraft designed by a single European nation has been steadily shrinking. Two disturbing trends also emerged: (1) despite the importance NATO places on equipment standardization, the variety of aircraft in the Central Region is higher now than it was in the 1950s, although it has declined slightly from its peak in the 1960s; and (2) the age of airframes in NATO's Central Region air forces has increased consistently, from roughly 4 years in 1950 to 15 years in 1990 — a reflection of the tendency to keep aircraft in national inventories longer. If current national plans were implemented, most of these trends would continue. The number of multirole and all-weather aircraft would increase. The variety of aircraft types would decrease. However, the average age of airframes would grow steadily, so that by 2005, average airframe ages would range from 18 to 29 years.