Abstract: An increase in the reliability of high-speed ultrasonic testing of elongated objects, in particular, railroad rails, is considered. It is shown that the current regulatory documents do not take into account the features of high-speed testing of rails, are focused on compliance with the initially specified parameters, and cannot provide the required reliability of defect detection. The factors that appear at high scanning speeds and negatively affect the quality of testing are considered. Most of these factors cannot be quantified to account for them and appropriately adjust testing parameters. The possible under rejection of defects when working in accordance with the current requirements has been assessed. To ensure more reliable testing in unpredictable and dynamic conditions of high scanning speeds, it is proposed to evaluate the current testing sensitivity by analyzing signals from typical structural reflectors of the test object. When inspecting rails, it is possible to use typical holes in the area of bolted joints that are regularly encountered along the scanning path as such reflectors. An expression is obtained for determining the magnitude of the correction of testing sensitivity taking into account the scanning speed and the measured parameters of the signals from the holes. An algorithm for dynamic correction of the testing sensitivity is proposed that increases the reliability of defect detection under high-speed scanning conditions.