July 31, 2007: As the U.S. Air Force and the American Congress battle over a replacement for the aging KC-135 tanker fleet, there are a large group of fans pulling for the KC-767 to become the new in-flight refueling aircraft. These fans are soldiers, sailors, marines and airmen who frequently fly as passengers on the hundreds of KC-135s that are still in service. The KC-135 has a cargo hold that is often stuffed with six standard cargo pallets, as well 80 passengers. It's kind of crowded when there are passengers and cargo on board, but the troops still consider the KC-135 a superior ride to the C-130, which normally does most of the short range runs (like from Germany to Rumania to the Persian Gulf.) The KC-767 will carry up to 200 passengers in considerably more comfort, or a hundred people if cargo pallet are also on board.

Unfortunately, there are several candidates for replacing the KC-135. The KC-767 is based on the Boeing 767-200 airliner, which sells for about $120 million. The Boeing 767 transport has been in service since 1982, and over 800 have been manufactured so far. Boeing developed the KC-767, at a cost of nearly a billion dollars, on its own. Boeing also developed the original KC-135 tanker in the 1950s, and has since built over 2,000 aerial tankers.

The four engine KC-135 carries 90 tons of fuel and can transfer up to 68 tons. To put that into perspective, a B-52 carries over 140 tons of jet fuel, and an F-15, over five tons. A two engine KC-767 carries about as much fuel as the KC-135. The European firm Airbus, is offering the KC-30, based on the Airbus 330-300, which normally sells for $160 million each. The KC-30 carries 20 percent more fuel than the KC-767, and more cargo pallets (26 versus 19). The troops won't mind if the KC-30 wins the current competition, because it is also based on a modern passenger jet.

The KC-135 has long made itself useful carrying cargo and passengers, as well as fuel, and both the KC-767 and KC-30 have more capacity for this. Another option is a tanker based on the larger Boeing 777-200LR, which sells for about $230 million each. This KC-777 would have 65 percent more fuel capacity than the KC-767, and 95 percent more cargo capacity.

Bigger is sometimes better if you're a flying gas station. But the KC-767 was developed partly because it is about the same size as the KC-135 (wingspan is 156 feet, ten more than the KC-135). Thus the 767 could use the same basing and repair facilities as the 135. The wingspan of the KC-777 would be 213 feet. Moreover, it would take about three years to develop the KC-777, while the KC-767 is ready to go now. The KC-30 will enter service with Australia next year. Using the KC-777 would reduce the number of tankers needed from 179 to 120, or less, and be cheaper in the long run.