After four decades of service, the U.S. Air Forces first specially built jet transport, the C-141, has been retired. The last flights took place on September 16, although twenty aircraft will continue operating in a reserve unit until 2006. The first C-141 unit became operational in 1965. A total of 284 C-141s were built between 1963 and 68. The C-141 was also the first jet transport able to drop paratroopers. The aircraft flew nearly nine million hours over the years. Originally, the C-141s were to be retired by 2003, but the Iraq war kept the aircraft flying a little longer. Between 1979 and 1982, most C-141s were upgraded from A to B standard. This included lengthening the aircraft 23 feet, which increased cargo capacity about a third. The max takeoff weight of the B model was 146 tons. Max load is 31 tons (or 200 troops, 155 paratroops or 103 litters and 14 seats.) Normal crew was five (two pilots, two flight engineers and one loadmaster.) For air drops, a navigator was usually carried. The C-141 has been replaced by the larger (265 tons) C-17. This aircraft is more flexible and can carry up to 76 tons and has a crew of only three (two pilots and a loadmaster.) Both the C-141 and C-17 had unlimited range via in-flight refueling.