Answer: A lot! Although it might not be as big as the Antonov An-225 Mriya, it sure is one hell of a cargo plane.
The first C-5 plane got made by Lockheed, and got delivered in 1969. To this day there are still a lot of them flying, but in military use only.
For a journey from the USA to Iraq it needs to be refueled 2 times. And the plane is so heavy that the tires need to be replaced after 8 flights only.
The Lockheed C-5 Galaxy has the largest lift capacity of any US transport aircraft, and the 3rd largest in the world. It is able to carry 122 tons on 2 decks, lower deck for cargo and the upper deck has seating for 73 passengers. It is a monster, but that is hard to put into perspective.
A C-5 Galaxy can hold 10 light armored vehicles, which at 12 tons each, aren’t very light at all. But lets get a bit more ambitious.
An Apache helicopter gunship is formidable weapon of war, and the C-5 can carry 6 of them. But empty of fuel and munitions they are fairly light, so lets get heavy.
An M1 Abrams main battle tank weighs 67 tons, and this monster aircraft can carry two of them. Or 1 Abrams and 2 Bradley IFVs. That’s all well and good, but what if you want a transport aircraft in your transport aircraft?
The C-5 can swallow an entire Chinook transport helicopter inside it. But what if you want to transport 30mm depleted uranium shells at 1000+m/s into enemy armour?
Then you’ll need one of these. A Galaxy can carry an A-10 Warthog, abet with the wings and tail detached, to wherever you need it to be. But an A-10 is pretty slow, so what if you want to go fast?
An F-14 is quite a bit faster than an A-10, and can fit nicely in the C-5’s belly. But just in case you need to bail out over the water, it might be a good idea to bring a boat.
A Mark 5 Special Operations boat might be what you want. An entire boat is impressive, but for the finale we need to go really meta…
The fuselage of a C-130 transport aircraft can be carried around by this monster of the skies.