A couple of issues on planes
* As someone mentioned, when configuring, it makes no difference how many seats you have. If I'm going to run a cargo airline, as has been suggested, then there's no way for me to configure an MD-81, say, as cargo-only.
* Again after exploring the configurator, I'm unable find a plane that carries heavy cargo. Even a 747 doesn't.
* Finally, there aren't any cargo-only planes anywhere. Used or new.