Aerospace Instrument-Making Annotation << Back Backstepping Altitude and Pitch Control of a Low-Flying Unmanned Aerial Vehicle based on a Disturbance Observer Ji Yunpeng, Selezneva M.S., Neusypin K.A. An aircraft that can fly low over the sea is a special type of aircraft that can perform certain functions above the sea surface. However, due to the roughness of sea waves in extreme situations, measuring the relative distance between the aircraft itself and the sea surface makes it difficult to control the system. In this paper, a mathematical model of the flight in altitude and pitch of an aircraft is constructed taking into account the external disturbance caused by the height of the sea waves. A control method was developed that synchronizes the Backstepping theory and the disturbance observer to ensure the stability of the system. Later, the stability of the designed method was proven using the Lyapunov theory, and the simulation results showed the effectiveness of the Backstepping method based on the disturbance observer. Keywords: disturbance observer, aircraft, backstepping control, flying over the sea, Lyapunov theory. DOI: 10.25791/aviakosmos.8.2025.1498 Pp. 23-36.