The Northrop F-5A/B Freedom Fighter and the F-5E/F Tiger II are part of a family of widely used light supersonic fighter aircraft, designed and built by Northrop. Although less complex and advanced than some contemporary aircraft such as the McDonnell Douglas F-4 Phantom II, it was significantly cheaper to procure and operate, and the type became a popular aircraft on the export market. While not procured in volume by the United States, it was perhaps the most effective air-to-air fighter possessed by the U.S. in the 1960s and early 1970s. Strengths included the aircraft"s compact size, a high level of maneuverability, favorable flying qualities and a low accident rate, and a high sortie generation rate. The capabilities, reliability, and maintainability of the F-5, similar to a Soviet counterpart, the Mikoyan-Gurevich MiG-21, led to hundreds of F-5s remaining in service into the 21st century.