During this mission, if Morello escapes and enters the airport he will get on a plane. Paulie tells you to shoot the plane down with his Thompson. Shoot at the engines on its wings. If you still miss the plane and it flies away from you, you will have to do it again. However when it flies off and Paulie tells Sam to shoot it down, press ACTION. You will be told to return to Salieri's bar. The mission will be completed and you will not need to repeat it.