Lockheed built just over one hundred C‑5 Galaxies; most now fly as upgraded Super Galaxies

Over time, Lockheed upgraded many of these aircraft to the C-5M Super Galaxy standard through the Reliability Enhancement and Re-engining Program that began in 2006. This upgrade included new General Electric F138-GE-100 engines and enhancements to various systems. The Super Galaxy has increased thrust by 22% compared to earlier models and can take off from shorter runways while carrying heavier loads.

The United States Air Force currently operates a fleet of 52 upgraded Super Galaxies, with additional aircraft stored at Davis-Monthan Air Force Base. Most original C-5As have been retired or are used for spare parts; only two modified for outsized cargo remain active.

Despite plans for passenger and cargo civilian versions under the L-500 designation—which could have carried up to 1,000 passengers—Lockheed was unable to secure orders due partly to competition from Boeing’s more successful civilian jets like the Boeing 747.

The development history of both companies is intertwined: Boeing originally designed its large jet transport as part of the same military requirement but ultimately lost out when Lockheed’s design was selected by the Air Force. Boeing repurposed its concept into what became the highly successful commercial Boeing 747 series—producing over 1,500 units compared with Lockheed’s much smaller output—and even adapted it for multiple roles including freighter operations and as a shuttle carrier aircraft.

Today’s U.S. strategic airlift fleet consists mainly of modernized C-5Ms alongside smaller but more numerous C-17 Globemaster IIIs and tactical C-130 Hercules variants for shorter missions. Occasionally, foreign-operated Antonov An-124s are contracted for oversized deliveries when needed.

While Lockheed Martin no longer produces passenger airliners like it once did with models such as the L-1011 TriStar (introduced in the early seventies), its legacy continues through ongoing service life extensions on military platforms like the C-5M Super Galaxy—expected to serve well into the next decades without any announced replacement program by the U.S. Air Force.