Method for debugging operational software of a system onboard an aircraft and device for implementing the same

The invention relates to a method for debugging the program of operational software of an onboard system, characterised in that it comprises the following steps: a) flagging (31) the program by positioning flags along an execution path for dividing said execution path into adjacent functional intervals; b) normal execution (32) of the program; c) acquiring (33) an execution condition of the program by flag condition vectors; d) when an error is detected, searching (36) a faulty functional interval based on the flag condition vectors, reverse execution (41) of the program in said faulty functional interval, and determination and correction of the error (42).