The U.S. Navy recently retired its last C-9B transport aircraft. The C-9s are actually DC-9 airliners converted to serve as 23 C-9A medical evacuation aircraft for the air force and 29 C-9B convertible personnel/cargo aircraft for the navy and marines. There were also three converted to be VC-9C VIP transports for the Department of Defense and two were purchased by Kuwait as C-9Ks. All of these have now been retired except for two C-9Bs still in use by the marines. The C-9 weighed 49-52 tons (depending on type) and could carry up to 16 tons of cargo or over 120 passengers. The C-9 entered service in the 1960s and 70s although the navy bought twelve second hand DC-9s in the 1980s and converted them to C-9s.
The DC-9 was very popular once it entered service in 1965. Nearly a thousand were built before production ceased in 1982. The DC-9 continued in production as the MD-80, MD-90 and Boeing 717 until 2006. Over 2,400 of all models were produced and hundreds are still in service. But the navy wanted a replaced for the C-9 and in 2001 the navy received its first C-40A transport. The navy has received a dozen C-40s so far. The C-40 is actually a Boeing 737-700C commercial aircraft. The plane entered service in 2001, and 19 have been built, eleven for the navy. The 78 ton aircraft carry 121 passengers, or eight cargo pallets (or a combination of both, usually three pallets and 70 passengers.) Max range is 5,600 kilometers. It normally carries a crew of five (two pilots, one crew chief, one loadmaster and one transport safety specialist, which is what the navy calls a flight attendant). When carrying just cargo, the flight attendant does not come along.
The C-40A is operated by navy reservists, and is mainly used to rush needed parts or personnel to where the fleet needs them. The C-40s also replaced the C-137 (a military version of the 148 ton B-707.) The navy is also using the 737 as the basis for its new P-8 maritime reconnaissance aircraft. The C-40 experience had a lot to do with the P-8 decision.