The U.S. government General Accounting Office GAO criticizes the U.S. Air Force agreement to lease 100 Boeing 767 aircraft, which will be configured as aerial tankers and called KC-767s. The GAO asserts that that the current fleet of KC-135E tankers are in good shape and that the air force could save over $12 billion by simply modernizing the KC-135Es. The air force contends that, with an average age of 43 years, the heavily used KC-135s are getting more difficult to maintain. The KC-135s are used more often than the nearly as old B-52s and it is generally agreed that aircraft that old will present more unforeseen problems. The 100 Boeing 767-200 ER aircraft would replace 126 KC-135Es. The air force also wants to adopt the 767 aircraft for all its support aircraft (reconnaissance, AWACs, etc) and this would get the process started. The 767 is also attractive because the large passenger cabin would be available to carry cargo or passengers. But the GAO does have a point that very old aircraft can remain in service with proper maintenance. Many Boeing 707s, the civilian version of the KC-135, are still in service. But it's telling that the many of groups still using 707s are African and Asian smugglers and gun runners. The GAO does nice work, but they tend to suffer from the "MacNamara Disease" (great analysis that largely ignores the people involved, like the KC-135 crews and maintainers.)