X-Plan is given to friends/neighbors of Ford employees... OR to Ford shareholders, special aviation club members, and there are some other ways of getting it. It's [0.996 * Dealer Invoice) + $75 or effectively invoice or a few bx under invoice. You give the salesperson your X-PIN (obtained either from a ford employee or through the membership at FAA or from Ford as a shareholder.
A-plan is for Ford employees (about $1500 under invoice or so), Z-plan is the same as A-plan but it is for retirees.
D-Plan is for Ford dealership employeees and is a few hundred more than A-Plan.