Tom Harris, writing in How Stuff Works, picks up the story of presidential planes from there: "President Truman took over the Sacred Cow, and later replaced it with a modified DC-6, which he dubbed the 'Independence.' Unlike the Sacred Cow, the Independence was covered in patriotic decoration, including an eagle head painted on its nose. President Eisenhower introduced two similar propeller planes, with upgraded equipment, including an air-to-ground telephone and an air-to-ground teletype machine.
"In 1958, presidential travel took a giant leap forward when the Air Force introduced two Boeing 707 jets into the fleet. The Air Force began using the radio call designation Air Force One during Eisenhower's administration, and the public took it up after Kennedy took office. At the beginning of his term, Kennedy added a more advanced, long-range 707, and oversaw an aesthetic redesign -- the blue and white decoration still used today.
"This plane and a twin added to the fleet in 1972 played a part in some of the most important historical events of the past 50 years. The 707 flew Kennedy to Dallas on November 22, 1963, and brought his body back later that day... The twin plane flew President Nixon from D.C. to California following his resignation. Mid-flight, the crew received confirmation that Gerald Ford had been sworn in as the next president, and they changed their radio call name from Air Force One to SAM (special air mission) 27000.
"The twin 707s served President Reagan throughout his two terms, and George Bush Sr. through the first part of his term. In 1990, the Air Force replaced the planes with the 747s in use today. The planes may be replaced again as early as 2010, when they hit their 20-year mark."