Abstract: A modal representation is developed for the acoustic pressure field in a stratified waveguide excited by a moving airborne source.In principle,the normal mode expression presented can be easily im-plemented in many underwater acoustic normal-mode codes.As an example,it has been implemented in Kraken based on the normal mode theory.Numerical results from Kraken are shown to be in accordance with those by OAST,a wave-number integration code.A physical explanation of the source/receiver mo-vement is given.