Theoretically you shoud add it to the cart and enter the cupon code as per below
Quote From FSPILOTSHOP
If you own a previous version of the Majestic MJC8 Q400, you can upgrade to this new 64-bit Pro version with support for Prepar3D v4 at a discount. Simply locate the product you have in your order history, then enter the coupon code shown during the checkout! In order for these coupons code to work, you MUST have the qualifying product in your order history. Be sure to verify the coupon has been applied before completing your order because adjustments and refunds are not available once the order has been completed.
You OwnCoupon CodeDiscountYou Pay
32-bit Pilot EdMJC832Pilot64Pro40%$53.95
32-bit Pro EdMJC632Pro64Pro73%$23.95
64-bit Pilot EdMJC664Pilot64Pro66%$30.00
The problem is: After adding it to the cart and entering the Cupon COde in the
"Gift Vouchers/Discount Coupons", there is a mesage saying that :
"Invalid Coupon Code, Please Check Code Again or Leave Blank"
Therefore, at least myself, I'm not able to conclude the transaction..
I will send a ticket to FSPILOTSHOP and wait for the solution.