This is the first of two papers describing the structure of northwest Pacific tropical cyclones as revealed by U.S. Air Force aircraft reconnaissance. This first paper describes the background philosophy for this research, the types of flight missions flown, data reduction procedures, and the general climatological characteristics of this region's typhoons and tropical storms. Analysis has been performed on 700 mb aircraft data from ova 500 Guam-based, WC-130 aircraft missions into 66 tropical cyclones, two-thirds of which were of typhoon intensity sometime during their life cycle. All flight missions followed similar standardized flight tracks. Data are analyzed for the three seasons of 1980–82. This aircraft dataset is unique in providing wind and pressure-height profile information at radial resolutions of 0.5° (56 km) from a tropical cyclone's center out to 4° radius. This allows a cyclone°s outer-core wind strength to be measured in relation to its inner-core intensity. The varying relations... Abstract This is the first of two papers describing the structure of northwest Pacific tropical cyclones as revealed by U.S. Air Force aircraft reconnaissance. This first paper describes the background philosophy for this research, the types of flight missions flown, data reduction procedures, and the general climatological characteristics of this region's typhoons and tropical storms. Analysis has been performed on 700 mb aircraft data from ova 500 Guam-based, WC-130 aircraft missions into 66 tropical cyclones, two-thirds of which were of typhoon intensity sometime during their life cycle. All flight missions followed similar standardized flight tracks. Data are analyzed for the three seasons of 1980–82. This aircraft dataset is unique in providing wind and pressure-height profile information at radial resolutions of 0.5° (56 km) from a tropical cyclone's center out to 4° radius. This allows a cyclone°s outer-core wind strength to be measured in relation to its inner-core intensity. The varying relations...