Though some people have reported success with the platinum card 2 for 1 vouchers, they are not really 2 for 1. That is because they will not allow the paid ticket to be discounted. However, you might still save something if the undiscounted ticket costs less than twice the discounted ticket. But your savings are likely to be in the $100s, not the $1000s.

Also, if you are intending to build miles by making purchases with your Amex platinum, neither AA nor United are part of their membership rewards program.