The U.S. Air Force has completed refurbishment of three of its 111 C-5 transports, and tests of this C-5M model indicate the upgrades (new engines, cockpit and electronics) have been successful. The air force plans to refurbish 52 of its C-5s to the C-5M standard. This will cost nearly $100 million per aircraft. The new engines are cheaper to operate, and quieter (max sound is 105 decibels, versus 120 with the old engines.) The new cockpit and electronics make the aircraft easier and safer to operate. The C-5Ms are expected to operate until the 2030s.
The C-5 entered service in 1970. It is a 380 ton aircraft that can carry up to 122 tons (but usually carries 100 tons or less, to reduce metal fatigue.) Max speed is 930 kilometers an hour. It can fly 4,400 kilometers on internal fuel, and can refuel in the air.