Mexican free-tailed bats (Tadarida brasiliensis) are believed to be the fastest moving mammals on Earth, reaching speeds exceeding 100 km/h during roost re-entry. Although the speeds of returning bats have been documented, the kinematics and echolocation behavior during high-speed flight are relatively unknown. Using a camera system synchronized to an ultrasonic microphone, we extracted the 3D position of 26 individual bats as they returned to their cave roost in New Mexico, USA. From the location of the body in each frame we determined instantaneous kinematic parameters including velocity, tangential and centripetal acceleration, flight curvature, and accelerations in terms of the gravitational constant g. Corresponding acoustic parameters including call duration, frequency, interval and time delay of received echoes were also calculated. Bats returned at speeds ranging from 10 to 22 m/s and max accelerations ranging from 2 g to 9 g. Based on curvature analysis of flight path, bats were further grouped into those that exhibited straight versus curved flight paths. For straight paths, bats shortened pulse duration and increased the frequency of calls as they approached the roost, whereas bats flying in curved paths demonstrated no overall change in acoustic signals. Furthermore, bats consistently produced calls at intervals above the time limit of call-echo overlap. Our results demonstrate that during high-speed flight, bats rely on their echoic stream to dynamically guide flight behavior.