I was asked to make some mini airplanes for toppers to cupcakes this weekend. I've made my marshmallow fondant...now what????? Help!!!!

Do you need them 3D or flat? Maybe looking at a few will get you going.

Some examples:

http://www.flickr.com/photos/clevercupcakes/3382589159/
http://www.flickr.com/photos/melovillareal/3049018215/
http://www.flickr.com/photos/47872669@N02/4589675173/
http://www.flickr.com/photos/33994534@N06/3585659569/
http://www.flickr.com/photos/23020485@N04/4038260607/
http://www.flickr.com/photos/cakesdusoleil/2489722143/

For children, I would say biplanes are better looking:
http://www.flickr.com/photos/bellescakefun/3476895658/
http://www.flickr.com/photos/bettyssugardreams/2842783170/

Are you meaning to model them as 3d figures? If so, doing them for today or tomorrow is really not much time for letting them dry! To make wings on an airplane, they will need to dry so they will stay out straight and not droop.

If you are planning 2D. You could probably cut yourself a template and use that to cut the shapes you need.