59 Dano
I just want to make friends!
It sounds to me like this would be a way to massively expand their prime offerings. Fly products around the country themselves and pass them off to the post office/Ground networks that will do last mile delivery. They don't need a full scale express operation, just enough to cut out the cost of express shipping.
The cost you say they're trying to cut out is the expense of air transport. That cost is still there whether they fly those packages FedEx/UPS or if they do it themselves. Currently, they share the expense of a flight with thousands of other shippers. If they do it themselves, they're on the hook for the entire bill.