a method and system for detecting errors in indicated air speed of an aircraft . the method may include receiving current measured data values indicative of one or more of a pressure altitude , vertical speed , pitch attitude , and engine power of the aircraft by a computer , accessing a table having values of indicated air speed corresponding to the current measured data values , and computing from the table and the current measured data values a current expected ias , receiving current data values indicative of measured ias of the aircraft , comparing the expected ias data values to the measured ias data values , and generating an alert signal when the expected ias data values and measured ias data values differ by a pre - set amount . the computer may include a software module that utilizes output from pre - existing on - board sensors , and may generate a signal to a crew alerting system .