International Child Visitation Schedule

[Neverenoughspoons]

I was hoping someone might be able to advise on a visitation schedule for my nephew to see his Mum. He is currently living overseas with his Mum and spends 2-3 nights a week with his Dad (my brother, who lives in the same City as them).
His Mum is moving to another country this Summer, and my nephew will be living full time with his Dad. We're trying to come up with a visitation schedule that covers all eventualities as communications are often very strained between his parents. So I feel it'll be better for everyone, especially my nephew if things aren't left open to interpretation.
The plan is that he will visit her twice a year ( he only gets 2 school holidays per year). He is under 10 so will need an adult accompanying him on the flights (long haul) for many years to come.
Any advice gratefully received!

Can't help with the visitation schedule, but Unaccompanied Minors scheme may assist with the flying. Emirates, for example, will take kids from 5yrs, and get them to a named adult at the other end (including transfers).

Thanks balloon. There is a scheme for unaccompanied minors with the airline they usually use, but my brother feels he's too young to use it at the moment.