The first thing that you need to consider is the purpose of your airplane lamp.
If you are looking for an airplane lamp that can add general illumination to the room, then what you are looking for is an ambient lighting type. For ambient purposes, look for a lamp that projects light to the sides and upwards.
If you are looking for a kind of lamp that helps you with your nighttime reading or any other task, then you are looking for task lighting. For this purpose, you'd want the lamp to project light downwards, and not upwards and sideward.
If you are looking for an airplane lamp purely for decorative purposes, then you don't have to worry about where the light is projected.