As a core subsystem of civil aircraft avionics, the Air Data Systems’ (ADS) output parameter accuracy directly determines the normal operation of the flight control system, navigation system, and display control panels. Inconsistencies in air data can easily lead to abnormal flight parameters and deviations in control commands, posing a serious threat to flight safety. It is a high-frequency and high-risk type of fault in route maintenance. This article focuses on this type of fault and explains the functions, components, and the entire workflow of data acquisition, calculation, and transmission of ADS on civil aircraft. Based on actual flight failure cases of relevant aircraft, this paper analyzes the causes of failures from dimensions such as hardware and circuits, and constructs a complete system of failure causes. The paper proposes effective solutions, including standardized fault localization processes, precise testing methods, and differentiated elimination strategies, forming a closed-loop solution of ‘diagnosis-localization-testing-verification,’ for failure characteristics caused by different reasons. This research can offer technical support for improving the operational reliability of civil aircraft ADS and reducing the recurrence of failures.