1. An aircraft flight management aid system configured to have access to a flight plan comprising initial constraints relating to respective parameters representative of an initial flight path that the aircraft is supposed to follow initially, characterized in that it is furthermore configured to have access to the effective values of said parameters, said values being representative of the path actually followed by the aircraft, said system comprising: means of interpretation capable of receiving data D relating to events likely to necessitate the following of a new path, different from the initial path, and of determining if they effectively necessitate the following of a new path, said data being taken from among: external instructions coming from an external control center, data relating to aircraft equipment failures, data relating to cabin problems, data relating to problems related to the environment of the aircraft; means of determination capable of receiving data D from the means of interpretation and of determining, at regular time intervals, at least one reference constraint associated with at least one parameter representative of a flight path, a reference constraint associated with a reference parameter comprising a new constraint, different from the initial constraint associated with this parameter when the means of determination have access to an item of data D relating to an event effectively necessitating the following of a new path, different from the initial path, and a reference constraint comprising the initial constraint associated with this parameter when the means of determination do not have access to any data D relating to an event effectively necessitating the following of a new path, checking means, capable of checking, at regular time intervals, from an effective value of said at least one parameter, if the path actually flown by the aircraft complies with said reference constraint associated with this parameter; and warning means capable of generating a warning to an operator when the path actually flown by the aircraft does not comply with said at least one reference constraint.