The 747 can be refuelled in mid-air and is therefore able to stay skyborne without landing for a long time.
Air Force One is stationed at Andrews Air Force Base in Maryland. Every time the President travels, a helicopter, Marine One, brings him from the White House to Andrews.
Until World War II not very many presidents travelled far away from their home country. Franklin D. Roosevelt was the first president to fly to a conference in Casablanca, Morocco.