For the first time, an ultrasonic flare gas flow meter demonstrates the accurate measurement of air flow up to 123.7 m/s. This new development could translate into higher flow-velocity flare gas measurement and monitoring, depending on the flare gas composition in an actual application. Abstract: Flare gas ultrasonic flow measurement has now been well established with more than 3000 units installed worldwide in process plants and refineries. One of the remaining technical challenges in flare gas ultrasonic flowmetering is to deal with extremely high flare flows (greater than 80 m/s) during emergency flaring. High flare flows introduce soaring flow noise, cause ultrasonic beam drift and thus deteriorate ultrasonic signal quality, leading to an ultimate failure of the flare gas flow measurement. In this paper, the ultrasonic propagation in flare gas has been studied, the beam drift due to gas flow has been investigated and improvements from both mechanical and transducer perspectives have been made. An improved flare gas ultrasonic flow meter has been developed to demonstrate the accurate measurement of air flow up to 123.7 m/s. Testing data have been presented for two typical configurations, Bias 90 and Diagonal 45, in comparison with a Venturi reference meter. The overall accuracy of the new flare meter is demonstrated to be 3-4%, and the relative standard deviation of the meter readings is within 1.2%. This new development could translate into higher flow-velocity flare gas measurement and monitoring, depending on the flare gas composition in an actual application.