The U.S. Air Force recently disclosed that, on average, 20 percent of its aging KC-135 tanker fleet is in the shop for long term maintenance. Not surprisingly, the air force asserts that, for some of the possible war scenarios (Korea, Taiwan/China), there would not be enough KC-135s to go around. This is largely because of the need to refuel navy aircraft. The navy can work around that, to a certain extent, by using U.S. Marine Corps KC-130 tankers and navy F-18 fighters equipped for the task. But this means the navy has fewer resources. The air force wants a new tanker, but incompetent procurement officials, and political interference in the process, have delayed that.
Meanwhile, the U.S. Air Force pays close attention to what happens to commercial air freight aircraft. That's because, while 42 percent of U.S. Air Force aircraft are over twenty years old, over eighty percent of those freighters are. The oldest are the KC-135s (which can also carry some freight). Operating aircraft this old is unexplored territory, because this is the first time in history that so many large, and fast, aircraft have gone on flying for so long.
The basic problem is that, despite constant maintenance and careful monitoring unexpected failures still occur with elderly aircraft. Nothing that is cause for alarm. Older aircraft are grounded if any unexpected failure seems imminent. While that just about eliminates these aircraft having fatal failures while in the air, it also makes older aircraft less available for service. But so far, it's been more cost effective to keep the old birds flying, than to buy new ones. Even growing fuel economy problems can be solved by installing new (more fuel efficient) engines. For the tankers, advanced age have made replacement a necessity, not an option.
Meanwhile, the leading replacement for the KC-135, the KC-767 is already in service with several foreign customers. While this is a bit of good news for the KC-767, this aircraft design is getting hammered by a competing design from Airbus. In 2002, the KC-767 was selected to replace the KC-135, but this was cancelled because of corruption in the procurement process. Two years ago, the air force selected the Airbus aircraft, called the KC-30 (based on the Airbus 330-300), over the KC-767. The KC-30 carries 20 percent more fuel than the KC-767, plus more cargo pallets (26 versus 19) and passengers. These were apparently decisive factors in the final decision. Legal action overturned the KC-30 selection, and there is now a new competition to choose a new U.S. tanker. Meanwhile the KC-30 MRTT (Multi-Role Tanker Transport) is getting more orders worldwide.
The KC-767 is based on the Boeing 767-200 airliner. The 767 has been in service since 1982, and over 800 have been manufactured. 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 of these. But the KC-767 sales effort was marred by the earlier use of bribes and other misbehavior.
The KC-135 replacement will officially be known as the KC-45A. The four engine KC-135 carries 90 tons of fuel and can transfer up to 68 tons. Typically, aerial tankers have to service B-52s, which carry over 140 tons of jet fuel, and fighters like the F-15 (over five tons). 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, with the KC-30 having a decisive edge.
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. That was not a critical factor. Moreover, Airbus has been developing the KC-30 for several years, and the first entered service with Australia last year.
The contract to build 179 KC-45As is worth about $35 billion (about $196 million per aircraft). Airbus offered to do nearly half the work in the United States and is still competing for the contract. Whoever wins, the air force won't begin receiving KC-45As for another 4-5 years.