In the European framework SESAR, the need to increase the air traffic capacity motivated the 4D (space + time) aircraft trajectory planning. In order to produce, a tactical trajectory planning (generating sets of 4D conflict-free trajectories), we use the Light Propagation Algorithm (LPA). This algorithm is based on a wavefront propagation method inspired from light propagation analogy. Besides, this algorithm is adapted to the trajectory planning problem. LPA produces very good results for a real traffic day over France, while satisfying specific ATM constraints. LPA was then adapted to take into account the uncertainties concerning actual aircraft positions. Once adapted to the uncertainty LPA was tested on the same traffic day. In order to enhance results obtained by LPA while considering uncertainty, RTA points (Real Arrival Time) are used. Indeed, when LPA fails to resolve conflicts, RTA points are imposed to aircraft trajectories, in order to reduce the uncertainty concerning aircraft positions. The obtained results are very encouraging.
