The paper deals with the problem of tracking program trajectory for the aircraft in the landing phase. Basic control law, synthesized according to the assumption that required state variables and external disturbances are known, is assumed as a basis for solving the problem of tracking in case of incomplete measurements. As a system of analytical reservation of board instruments, cascade system of state observers with corrective actions in the form of sat-functions was built. The system allows assessing both some of the variables of the state vector, and evaluation of external disturbances acting on the aircraft. For these procedures the simulation results are presented.