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Also, don't completely count out a "KC-380" that would also double as a large freighter.

There are good reasons why the A380 has been put on hold indefinitely. Despite its large volume, it can only haul 150 tons of freight. Also it has two freight decks requiring rare and specialized ground equipment at every airport it visits. It's only good for palletized or container freight due to the dimensions of the ceilings in the cargo holds. The floor between the first and second deck can not be removed to make space for oversized freight, because it is needed for structural rigidity. The floor of the upper freight deck can't support dense heavy freight complicating loading of an A380F. It is also structurally less efficient than the 747. The only criterion on which it beats a 747 is runway and climb performance and range with maximum payload.

A 747 has a very low ratio of Operating Empty Weight to Maximum Take Off Weight, and the 747-800 has even better structural efficiency than previous models. It has a single freight deck that can handle heavy and oversized freight, and it has a nose door to handle oversized items that otherwise can only be carried in military freighters like the C-5, C-17, and AN-124. The 747 has already been certified as a tanker back in the 1970's when Iran Air bought 747's that could be also used by the Iranian Air Force as tankers. It already has been modified for receiving refueling from tankers in the E-4B and VC-25 models. Potentially a 747 freighter could be built with the same upper deck as the 747-800I and have a large number of passenger seats. This would be quite useful for transporting specialists along with cargo on one aircraft. The 787-8 will be the fastest civilian passenger and cargo aircraft so on a transport mission to carry freight to bases near a theater, it can get where its going a lot faster than a C-5 or C-17. It's long range means it could perform some cargo hauling missions without refueling in the air and costing the Pentagon $17 a gallon for fuel.

It is also structurally less efficient than the 747.

While I agree that a KC-380 makes little sense, the claim that the A380 is structurally less efficient than the 747 is not exactly true. Because quite the opposite: it's very efficient as a passenger aircraft and with its ovoid cross section makes optimal use of its interior space - for passenger transport, that is. The pear shaped front end cross section of a 747 is a compromise when it comes to carrying passengers and carries a weight penalty. It's as a freighter that the 747 truly excells, because that was it's primary objective and that's when the design decisions make sense.

In short:
A380 - Efficient passenger hauler - mediocre freighter
B747 - Outstanding cargo aircraft - outdated for air travel.

I agree that the 747-8F would make an excellent freighter/tanker for the Air Force, but I still say a "KC-380" cannot be fully counted out, either.

I realize the tonnage issue, and that the A380F has two decks (three counting the cargo hold) that can only hold standardized pallets (the upper cabin floor in an integral fuselage structure that cannot be removed.) I've read Randy's Journal, too. ;^)

The A380F is optimized for max volume, while the 747-8F is better for outsized cargo. However, the 747-8F front load door is best only for outsized cargo. Most palletized cargo goes through the side doors, so the loading nose may not be put on a "KC-747." (The Air Force has lots of C-5s and C-17s for outsized cargo.)

In a Freighter/Tanker role, having an entire upper cabin for seating and the entire lower cabin (and cargo hold) for palletized freight isn't going to hit max gross weight before it hits max volume, and would allow an entire maintenance squadron deploy along with the air squadron, not just the flightline troops as is done with the KC-10 and soon to be KC-45.

There would only be a limited need for this size of an aircraft, thus it would only be purchased in KC-10 like numbers, i.e. 6 or 7 dozen vs. several hundred KC-45s.

Thank you all for more great information on options for the KC-380 versus the KC-747 versus the KC-777. I've plugged more numbers into a comparative spreadsheet to see how much fuel they each could offload at, for instance, 2400 nm away (and allowing they have to fly back to the US to themselves refuel -- 4800 nm round trip). 2400 nautical miles is the range of all three or our cargo airlift aircraft -- C-17, C-5, and C-130. 2400 nautical miles is about the distance from Delaware to the Azores, and again from the Azores to Greece, and again from Greece to Afghanistan. If our freight aircraft can't refuel in the Portuguese Azores, then we need tankers to get them across the Atlantic and over the Mediterranean where, hopefully we have friends who will let them refuel.

At 2400 nm the 777 could offload about 200,000 lbs of fuel and still fly home; the A-380 could offload about the same 200,000 lbs of fuel because it gets one-third the fuel mileage in spite of its greater capacity. The 747-8 would be able to offload about 300,000 lbs of fuel and still fly home to the East Coast. For comparison, the KC-45 (A330-200) has a total fuel capacity of about 250,000 lbs and the KC-10 about 350,000 lbs.

Bottom line -- we need a few hundred 747-8 tankers.
Or we need to make darn sure we have refueling bases every 2400 nm between the US and wherever we may need to send a few hundred cargo aircraft with troops and equipment which need to be on the ground with a few days instead of a few weeks (by sea).