The VC-25 (also known as 747-200) is most notable for its role as Air Force One, the callsign of any U.S. Airforce aircraft carrying the President of the United States. The VC-25 differs from the standard Boeing 747 relating to interior dimensions and security features. The VC-25 is capable of flying 7,800 miles without refueling and can accommodate more than 79 passengers. Each VC-25 cost approximately US$325 million. The VC-25 replaced the VC-137 as the mainstays of the Airforce One fleet. On some occasions, the planes are used to transport the Vice President of the United States, for which service they adopt the callsign Airforce Two. These aircraft are maintained and operated as military operations. The VC-25 can also be operated as a military command center in the event of an incident such as a nuclear attack. Operational modifications include aerial refueling capability and anti-aircraft missile countermeasures. The VC-25 has also been used to transport deceased former presidents. The remains of Ronald Reagan and General Ford were transported by SAM 28000 and 29000 respectively to Wsahington for their state funerals, and then on to their final resting places. The VC-25 replaced 707 as presidential aircraft of John F. Kennedy in 1990.