C-5 Galaxy vs C-17 Globemaster III: How the Airlifters Compare

The Lockheed C-5M Super Galaxy and the Boeing C-17 Globemaster III are the two aircraft the United States relies on to move heavy military cargo over long distances. They look similar from a distance and their top speeds are almost identical, but they were built to solve different problems.

The Galaxy is a strategic airlifter: the biggest load, the longest reach, base to base. The Globemaster is a strategic and tactical airlifter: a smaller load, but delivered much closer to where it is needed, including onto short unpaved strips. The measure you care about decides which one wins.

Full dimensions, weights, engine data and raw performance figures for both aircraft are in the database comparison at the top of this page. The table below covers what those specs do not: role, loading, basing, readiness and cost.

How we are comparing these two airlifters

Almost every “which is better” argument about the Galaxy and the Globemaster is really an argument about which job is being asked of them. The honest comparison names the measure first.

This article ranks them on four measures: how much they carry, how far they carry it, where they can land, and how much they cost to keep flying. The C-5 wins the first two. The C-17 wins the last two.

Where an official number exists we use it, mostly from the US Air Force fact sheets for each aircraft. Where figures move year to year, such as fleet size and readiness, we anchor them to 2026 and say so.

Where the C-5M Super Galaxy wins

Cargo volume and outsize loads

The Galaxy’s cargo compartment runs 143 feet 9 inches long, 19 feet wide and 13 feet 6 inches high, for just over 31,000 cubic feet of usable space. The Globemaster’s hold is 88 feet long, 18 feet wide and 12 feet 4 inches high.

That difference is the whole point of the C-5. It can load two M1 Abrams main battle tanks in one aircraft, where the C-17 carries one. It swallows helicopters with their rotors still on, mobile bridging, and other loads too long or too tall for the Globemaster.

Two C-5s, the modified C-5C variant, were even rebuilt to carry NASA payload containers for the Space Shuttle program. No other airlifter in the fleet was asked to do that.

Loading is faster too. Both the nose and the tail of the C-5 open, so ground crews can drive vehicles in one end and out the other. The nose visor hinges up and out of the way, and full-width ramps at each end take double rows of trucks. The C-17 loads only through its rear ramp.

Payload and range

The C-5M carries a maximum payload of 281,001 pounds (127,460 kg) against 170,900 pounds (77,519 kg) for the C-17. Maximum takeoff weight is 840,000 pounds (381,000 kg) for the Galaxy and 585,000 pounds (265,000 kg) for the Globemaster.

Range favors the C-5 as well. With a 120,000-pound load the Super Galaxy flies about 4,800 nautical miles unrefueled, and with no cargo it reaches roughly 7,000 nautical miles. Loaded to 281,001 pounds it can still fly 2,150 nautical miles, drop the cargo, and reposition 500 nautical miles further without tanking.

The C-17 has an unrefueled range of about 2,400 nautical miles carrying 164,900 pounds. Both aircraft take fuel in flight, so on a mission with tanker support the practical limit becomes crew endurance rather than fuel.

Where the C-17 Globemaster III wins

Short and unpaved runways

This is the capability the C-5 does not have. The C-17 can take off and land on runways as short as 3,500 feet and only 90 feet wide, including dirt and gravel strips near a front line.

Its high-lift wing, leading-edge slats and externally blown flaps let it fly a steep, slow approach into a small field. Once down, it can turn around on a 90-foot runway using a three-point star turn and reverse under its own thrust, so it never needs a taxiway or a tow.

The Galaxy needs long paved runways and the infrastructure of a major air base. That is why the two aircraft work as a pair: the C-5 hauls the load across an ocean to a hub, and the C-17 carries it the last few hundred miles to an austere strip.

Readiness and fleet size

Boeing built 279 C-17s between 1991 and 2015, and 222 of them serve with the active-duty Air Force, the Air National Guard and the Air Force Reserve. Lockheed built 131 Galaxies, and only the 52 that were re-engined and modernized into C-5Ms remain in service.

Availability is the wider gap. In fiscal year 2024 the C-17 fleet posted a mission-capable rate of 75.2 percent, one of the best in the Air Force. The C-5M managed 48.6 percent, held down by parts shortages for a design whose original suppliers have largely disappeared.

So on an average day the Air Force has more than 160 C-17s ready to fly and fewer than 30 C-5Ms. When airlift has to happen now, the Globemaster is usually the aircraft that goes.

Cost per flying hour

The Department of Defense’s FY2025 reimbursable rates, the hourly price one part of the Pentagon pays another to use an aircraft, put a C-5M flying hour at $34,499 and a C-17A hour at $19,515.

Those figures capture fuel and consumption-driven maintenance rather than the full ownership cost, but the ratio holds across most published estimates: a Galaxy hour costs roughly two-thirds to twice as much as a Globemaster hour. Four large engines moving 840,000 pounds is expensive, and the C-5’s maintenance burden is heavier per flight.

For a load that fits in a C-17, the C-17 is the cheaper way to move it. The C-5 earns its cost only when the cargo is too big or the distance too long for anything else.

How to tell a C-5 from a C-17

Both are high-wing, T-tail, four-engine jets in gray paint, so they are easy to confuse at an airshow. A few features separate them at a glance.

The C-5 is much bigger, at 247 feet long with a 222-foot wingspan, and its engine pods hang well forward of the wing. The nose looks blunt because the whole front of the aircraft hinges upward to open. Underneath, you can count 28 main-gear wheels.

The C-17 is 174 feet long with a 170-foot span and prominent winglets angled up at the wingtips, which the C-5 does not have. It has no nose door: every load goes in through the rear ramp.

Is the C-17 bigger than the C-5 Galaxy?

No. The C-5 Galaxy is substantially larger on every axis: longer fuselage, wider span, taller tail, heavier maximum weight and a far bigger cargo hold. The C-17 is the more capable aircraft in several ways, but size is not one of them.

Only a handful of aircraft have ever been bigger than the Galaxy. The Antonov An-124 Ruslan outweighs it, and the one-off Antonov An-225 Mriya, destroyed in 2022, was larger again. Among aircraft still flying and in production, the C-5 remains one of the largest in the world. Our guide to the largest cargo planes puts all of them in order.

Why was the C-17 discontinued?

Boeing ended C-17 production in 2015, and the final aircraft left the Long Beach, California assembly plant on November 29 that year. The line closed after 279 aircraft.

This was not a failure of the design. The Air Force had received all 223 aircraft it planned to buy, US deliveries had finished in 2013, and foreign orders had run out. With no more customers, Boeing could not justify keeping the plant open, and about 2,200 jobs went with it.

Because the tooling and supply chain are gone, the C-17 cannot simply be restarted. The current fleet is being sustained and upgraded instead, with a planned service life stretching toward the 2070s. The C-5M is expected to fly into the 2040s and possibly to 2050.

Where the C-130 fits

People often search for the C-5, the C-17 and the C-130 together, but the Hercules is a different class of aircraft. It is a turboprop tactical transport that carries around 42,000 pounds, roughly a quarter of a C-17 load, into the smallest and roughest strips of all.

The three form a chain: the C-5 moves outsize cargo between continents, the C-17 takes strategic loads into theater and onto austere fields, and the C-130 Hercules handles the short tactical hops. We break the smaller pairing down in C-130 vs C-17 and C-5 Galaxy vs C-130 Hercules.

The verdict

If the cargo is enormous and the trip is intercontinental, the answer is the C-5M Super Galaxy. Nothing else in the US fleet moves that much mass that far in one aircraft, and its drive-through loading and outsize hold have no substitute.

For everything else, the C-17 Globemaster III is the better choice. It carries most military loads, lands where the Galaxy cannot, is ready far more often, and costs less per hour to fly.

The US Air Force did not pick one. It uses the Galaxy to carry the heaviest loads across the world and the Globemaster to deliver them the rest of the way, and that split is the real answer to C-5 versus C-17. For the wider field, see our rankings of the biggest military airplanes and the types of cargo planes in service.