Leaders and dignitaries from around the world will travel to South Africa this week to attend memorial services for Nelson Mandela, the man that many call tata or father. The memorial service held on Tuesday will also mark a rare occasion when nearly all of the living presidents gather together. The President and First Lady are traveling today and will be joined on Air Force One by former President and first lady – George W and Laura Bush. Presidents Clinton and Carter will travel separately. President George H.W. Bush is too ill to travel the long distance.