Search Lego and collect the published bricks. Then start assembling...
http://communities.ptc.com/photoAlbums/1295
Otherwise, this is a question that is way to open to easily answer. Extrudes, Sweeps, and blends will go a long way to making something that resembles an airplane...
It might be a good idea to tell us what purpose the model will be used for.
My first reaction was that modelling a whole aircraft is a bit ambitious... I suspect that at Boeing, it takes hundreds of people several years to do this, so you might be better starting with something that has less than, say, 100 000 components. 
However, I'm guessing that what you actually want is just an external representation of an aircraft.
Really, it's better to learn the basic tools that Pro/E (sorry, Creo) offers, and then you can start using those to model anything you want - in any level of detail you want. 
Although Antonius' balsa plane might be a good early tutorial!
.... or the kinds with the flimsy wheels on the wire, the hook, rubber band and whirlie bird propeller for added components.
