This instructable will show you how to make and a mold and how to fill it with molding epoxy. You don't have to use an airplane. This is just what I am using to show you how to make the mold.
Step 1: Mixing Ingredients
First, find a pour able silicone rubber used for making molds (found at any craft store). Then, mix the ingredients as shone on the box of the molding material.
The next step is to get a casting epoxy, and mix it according to the directions.
Step 2: Molding
Once you have the molding material, quickly cover the item you wish to mold leaving the one end open to pour the epoxy. (You may want to fill mold with water to find leak)
Once the rubber has dried, pour the epoxy into the mold and wait until the epoxy sets (may vary with different products).
Step 3: Removeal
Carefully remove the item from the mold (once set), and now you can mass produce items in your own home!