The crew member needs to discuss his concerns with the charter company, and they should clarify their obligations with their immigration lawyer. It is possible that they don't understand that immigration issues are involved, particularly if they have only one foreign national working on the crew, or that they believe that they can sidestep visa and immigration issues by simply treating everybody on board as an independent contractor.

If the charter company won't take that step, the crew member may need to reconsider whether or not he wants to take the job. Frankly, it sounds like he should be using a transit visa, not a tourist visa.