If FDX continues to tank, they've got a large aircraft fleet and facilities that could be a real bargain for Bezos if he wants to expand into Express common carriage or further expand his Prime coverage and capabilities.
More importantly, they have landing slots and routes. If you recall, the 1989 Flying Tiger purchase was all about landing rights and slots, not Tigers itself.
The desert is full of freighters right now, most of them fuel hogs and/or obsolete. When you start parking newer more fuel-efficient freighters, and you can buy jet fuel futures for peanuts and lock them in, there are lots of possibilities.