Formally, there's the Civil Reserve Air Fleet https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet and in

Formally, there's the Civil Reserve Air Fleet https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet and in general these planes can be used in emergencies. The transport planes the US military tends to buy have additional requirements that aren't conducive to civil air fleet profitability.