Not any different than what World was doing. Doing ACMI for another offshore carrier that could not operate into the U.S. under part 129. The reason for the dispute is not clear, but World appears to be disputing on the U.S. side to either keep Sonair tied to them or they may actually attempt to start their own flights. Kind of doubt the latter though.
I did the same thing flying for a U.S. carrier that did ACMI for a Central American carrier that did not qualify to operate into the U.S. in the past. As a matter of fact, we did it for a couple of different carriers using their FA's (after receiving our carriers training), our U.S. pilots, U.S. airline certificate and A/C. Even leased a couple of their A/C and put it on our certificate and MX program.