In previous events, they made special arrangements for those that were truly unable to fly (e.g. medical reasons). It usually involved having to wait for space on another cruise ship stopping in that port that was sailing back to the mainland. I know in previous events Carnival put people on RCCL and NCL ships that had availability. I imagine NCL is doing the same. But those people would definitely have to make sure NCL was aware of their issue, because the general expectation will be that you will be accommodated on those charter flights.