The KC-135 Stratotanker may be best known as the world's flying gas station because of it's roll in providing aerial refueling support to the U.S. Air Force, Navy and Marine Corps aircraft, as well as planes of allied nations. These tankers are modified Boeing Company 707s and can carry up to 200,000 pounds of fuel for transfer. The KC-135 has a top speed of 530 miles per hour and a ceiling of 50,000 feet. Refuelings can take place at altitudes ranging from a few thousand feet to 20,000 feet or more, depending on the mission. The KC-135 was first deployed in 1956 and current inventory includes 195 aircraft in active duty, 251 in Air National Guard duty and 84 in the Air Force Reserve.
The Stratotanker is currently in the process of being gradually withdrawn from Front line service with the USAF. Two of the four squadrons of the 319th Air Refuelling Wing, which has operated the type since 1962, have already been deactivated with the other two planned to follow from June 2009.