1 I got on the plane : it is the prétérit of the get .we use the prétérit to talk about an action that took place in the past and that is finished .you should say : yesterday I got on the plane 2 i’ve Got on the plane : the use of the present perfect refers to an action that is CONNECTED to the present ..you should say I have JUST got on the plane ....for example if you are on the plane talking to a friend on the phone . So always think if the action took place in the past or is connected to the present situation you are living Good luck