A device for aiding the piloting of an airplane during a phase of landing on an airport, said device being provided with an automatic braking system which is able to automatically brake the airplane during the ground rollout on a landing runway, said braking system comprising: - a flight controls computer, for computing a nominal deceleration making it possible, when it is applied to the airplane, to stop it level with a selected exit on the landing runway; and - a braking computer, for computing, on the basis of a deceleration received, commands for control of braking means of the airplane, characterized in that: - said device moreover comprises: • first means for providing data exhibiting a rate of occurrence of error or of alteration which is compatible with safety objectives required on an airplane during a landing, said data comprising at least one of the following data: - a value of ground speed of the airplane; - an estimation of the distance between the airplane and the threshold of the runway used for landing; and, optionally: - a value of length of the runway used for landing; • second means for computing, on the basis of said data, a minimum deceleration making it possible to ensure that the airplane stops before the end of the landing runway, when this minimum deceleration is applied to said airplane; and • third means for comparing said nominal deceleration with said minimum deceleration and for transmitting the higher deceleration to said braking computer; and - said second and third means (13, 14) form part of said flight controls computer; - said first means comprise a plurality of inertial reference systems (19A to 19N) able to generate ground speeds of the airplane, as well as passivation means for providing a ground speed as given data, solely in the case of consistency between the ground speeds arising respectively from said inertial reference systems (19A to 19N); and - said first means comprise means which are integrated into said flight controls computer and which are formed so as to estimate the distance between the airplane and the threshold of the runway used for landing, by integrating a ground speed. - a flight controls computer, for computing a nominal deceleration making it possible, when it is applied to the airplane, to stop it level with a selected exit on the landing runway; and - a braking computer, for computing, on the basis of a deceleration received, commands for control of braking means of the airplane, characterized in that: - said device moreover comprises: • first means for providing data exhibiting a rate of occurrence of error or of alteration which is compatible with safety objectives required on an airplane during a landing, said data comprising at least one of the following data: - a value of ground speed of the airplane; - an estimation of the distance between the airplane and the threshold of the runway used for landing; and, optionally: - a value of length of the runway used for landing; • second means for computing, on the basis of said data, a minimum deceleration making it possible to ensure that the airplane stops before the end of the landing runway, when this minimum deceleration is applied to said airplane; and • third means for comparing said nominal deceleration with said minimum deceleration and for transmitting the higher deceleration to said braking computer; and • first means for providing data exhibiting a rate of occurrence of error or of alteration which is compatible with safety objectives required on an airplane during a landing, said data comprising at least one of the following data: - a value of ground speed of the airplane; - an estimation of the distance between the airplane and the threshold of the runway used for landing; and, optionally: - a value of length of the runway used for landing; - a value of ground speed of the airplane; - an estimation of the distance between the airplane and the threshold of the runway used for landing; - a value of length of the runway used for landing; • second means for computing, on the basis of said data, a minimum deceleration making it possible to ensure that the airplane stops before the end of the landing runway, when this minimum deceleration is applied to said airplane; and • third means for comparing said nominal deceleration with said minimum deceleration and for transmitting the higher deceleration to said braking computer; and - said second and third means (13, 14) form part of said flight controls computer; - said first means comprise a plurality of inertial reference systems (19A to 19N) able to generate ground speeds of the airplane, as well as passivation means for providing a ground speed as given data, solely in the case of consistency between the ground speeds arising respectively from said inertial reference systems (19A to 19N); and - said first means comprise means which are integrated into said flight controls computer and which are formed so as to estimate the distance between the airplane and the threshold of the runway used for landing, by integrating a ground speed.