The U.S. Air Force retired its last C-5A transport in early September. The C-5 is still in service as a much modernized C-5M. The first production version of the C-5M transport entered service in late 2010 while the last of the 52 refurbished C-5Ms arrived in 2017. These are expected to service until 2040. About the same number of older C-5s were retired to the air force “bone yard” where they were used for spare parts or scrap.
The C-5M upgrades (new engines, cockpit and electronics) proved to be more successful than expected. The refurb also replaced any worn structural components, replaced existing engines with more powerful and fuel efficient ones, and installed new electronics. This included digital controls, a much nicer looking cockpit, all-weather capability and better communications. The C-5M is easier to handle than the older models, and costs a third less to fly as well. The upgrade costs about $120 million per aircraft. While the M model can carry more weight over longer distances, that was not the main goal of the upgrade. The primary objective was to create an aircraft that was cheaper to fly and operate, and was more reliable and easier to maintain. The new engines are not only cheaper to operate but also much quieter (max sound is 105 decibels, versus 120 with the old engines.) The C-5As were notable for the distinct engine sound, which is now gone forever.
The C-5A entered service in 1970 and production ended in 1973 with 81 delivered. It was a 380 ton aircraft that could carry up to 122 tons (but usually 100 tons or less, to reduce metal fatigue.) Max speed was 930 kilometers an hour. It could fly 4,400 kilometers on internal fuel, and refuel in the air. The C-5M refurbishment program is considered the last one and is actually a culmination of an upgrade program that began in the 1980s when C-5 production was resumed as the C-5B with 50 delivered by 1989. Thus the total production of C-5s was 131 aircraft.
While the C-5 had many technical problems that were addressed in numerous upgrades, there were also political problems. In 2009 the U.S. Congress finally agreed to let the U.S. Air Force retire its oldest air transports. The air force had 59 elderly C-5As, that were introduced in the early 1970s, and Congress insisted they be kept flying because otherwise some key legislators would lose jobs in their districts. Keeping these old aircraft in the air was getting so expensive, that it became embarrassing to Congress, and the air force was allowed to retire them. There were still 52 C-5Bs models, built in the 1980s, that had some (economically) useful life left in them. Congress agreed to have these upgraded to C-5Ms. Before the latest decision, the air force was going to spend a lot of money upgrading the C-5As. But now the air force could build more C-17s instead.
Before 2009 the air force looked into a replacement for the C-5. The most attractive proposal was a military version of the already planned freighter version of the new Airbus 380. While the C-5 can carry up to 122 tons of cargo on one deck the 380F could carry up to 150 tons of cargo on three decks. At that point (2007) Airbus already has 25 orders for the freighter version. The first passenger version of the 380 had just entered service. Boeing offered the latest version of the 747, the 747 8F, as a C-5 replacement. This aircraft can carry 140 tons in 854 cubic meters of cargo space. Neither of these proposals worked. The 380 freighter was never built because it turned out it was not economical to operate. The passenger version of the 380 entered service but demand was not what Airbus expected. The Boeing 747 8F was more successful commercially and entered service in 2011 and is still in production with 71 in service by 2017. The 747 8F can carry 132 tons on a single deck. But the 787 8F needed some modifications for military service and it was feared these would drive the cost per aircraft to nearly half a billion dollars each. As it is the 747 8F already cost $380 million each and the experience with “militarizing” commercial transport for military use indicated the process could be time-consuming as well as expensive.
Meanwhile it turned out there was a market for larger air transports, just not for a lot of them. This was demonstrated with the Russian (now Ukrainian) An-124. The An-124 is the world's largest production aircraft and can carry a payload of 120 tons and had a lot more interior volume than any other transport. It first flew in 1986 and only 55 have been built so far. New ones will cost over $100 million each. Russia has been trying to get it back into production for over a decade but needed to work out a deal with Ukraine, where the An-124 is built. In 2103 Russia and Ukraine had worked out a deal to build 20 new commercial An-124s but the contract had not been signed yet. Apparently a contract to build ten new An-124s for the Russian Air Force was closer to signing but that deal was cancelled when Russia went to war with Ukraine in 2014, a conflict that is still unresolved. The Ukrainian manufacturer wanted to build new aircraft as An-124-150s and upgrade some existing ones to that standard. That would reduce crew size from six to four and increase carrying capacity to 150 tons. The An-124 has been very successful as a commercial transport, especially for military purposes. Even NATO leases An-124s for moving military cargo. Ukraine needs the work and Russia needs the An-124s but until the current conflict is resolved that will all have to wait.