In this study, the longitudinal stability derivatives of a transport aircraft have been calculated by modeling the aircraft configuration and flight condition. The applying method is able to use for all sizes of civil and military aircrafts. As a second step, the longitudinal motion of aircraft is investigated and the transfer functions of linearized equations of motion have been obtained. Phugoid and short period modes have been investigated. Frequency-response and transient-response analysis have been performed respectively by using Matlab Simulink.