I've heard many stories of people in this situation who move to a furnished apartment near the hospital so that they can be there as soon as they get the call. Depending on commercial flights in this sort of situation is just too risky. Even charter flights carry the risk of weather or mechanical delays. I understand that it's very difficult to pack up your life and move to another city for possibly months at a time, but it would probably be the safest bet since his life actually depends on it.