Before choosing your plane on the list, hold the right ALT, SHIFT and CTRL keys.
Extra Objects
For extra objects in "Create Pro Mission," hold down the right ALT, SHIFT and CTRL keys, then click on the Create Pro Mission. Keep holding the ALT-SHIFT-CTRL and click on the OBJECTS menu and then click on ALL. You'll now have 34 pages instead of 33.
Pro Mission Editor
Hold down right ALT-SHIFT-CONTROL in the main menu and select PRO MISSION EDITOR. Once in the editor, hold right ALT-SHIFT-CONTROL again and go to FILE/LOAD MISSION. This will allow you to select many more missions to edit.