Speed (km/hr) during flight is one of several factors determining the rate of migration (km/ day) and flight range of birds. We attached 26-g, back-mounted satellite-received radio tags (platform transmitting terminals; PTTs) to adult female Northern Pintails (Anas acuta) during (1) midwinter 2000–2003 in the northern Central Valley of California, (2) fall and winter 2002–2003 in the Playa Lakes Region and Gulf Coast of Texas, and (3) early fall 2002–2003 in south-central New Mexico. We tracked tagged birds after release and, in several instances, obtained multiple locations during single migratory flights (flight paths). We used data from 17 PTT-tagged hens along 21 migratory flight paths to estimate groundspeeds during spring (n = 19 flights) and fall (n = 2 flights). Pintails migrated at an average groundspeed of 77 ± 4 (SE) km/hr (range for individual flight paths = 40–122 km/hr), which was within the range of estimates reported in the literature for migratory and local flights of waterfowl (42–116 km/hr); further, groundspeed averaged 53 ± 6 km/hr in headwinds and 82 ± 4 km/hr in tailwinds. At a typical, but hypothetical, flight altitude of 1,460 m (850 millibars standard pressure), 17 of the 21 flight paths occurred in tailwinds with an average airspeed of 55 ± 4 km/hr, and 4 occurred in headwinds with an average airspeed of 71 ± 4 km/hr. These adjustments in airspeed and groundspeed in response to wind suggest that pintails migrated at airspeeds that on average maximized range and conserved energy, and fell within the range of expectations based on aerodynamic and energetic theory.