World operates many cargo flights from Lej --mostly to JFK for Lufthansa Cargo. If not mistaken had done some to Chicago as well although I think that ended or is all from Frankfurt.
Both N. American and World use Lej as a tech stop or mini hub for the AMC passenger flights so there is always something going to USA just the times and destinations are slightly different. World normally has one Airplane that shuttles back and forth from DFW, ATL to LEJ and Kuwait and then the rest to various locations or bases in US.
Call World Dispatch 770-632-8030 to list.
I believe you need to list with dispatch at least 24 hours prior on the international flights.
As long as your part 121 i believe you can jumpseat even on the military flights and cargo is pretty relaxed...up until recently we used to be able to even bring family/friends if ac had courier seats but that has changed to our own crews, including FAs and other part 121 pilots.
If you have any other questions I will try to find the answer and hopefully somebody from NAA can fill you in on their process.