A displacement system for an airplane seat comprising a sitting portion, a backrest and a legrest, the displacement system comprising a support structure, a sitting portion structure connected to the support structure on a first plane (α), and a kinematic mechanism for displacement acts on at least the sitting portion structure to pass between a first sitting configuration and at least a second cradle configuration and vice versa, a surface of the sitting portion comprising at least a first back portion lying on the first plane (α), and a second front portion lying on a second plane (β), the portions being constrained in rotation with each other in passage between the first configuration to the second configuration, and vice versa, the kinematic mechanism for displacement being configured to act on the second portion so that, in different configurations, the second portion is inclined at different angles with respect to the first portion.