USAF Tail #s are based on the fiscal year in which the airframe was purchased and typically look, officially, something like 53-4118. This example would be the 4,118 airframe purchased in fiscal year 1953.
Sometimes, like in your case, they drop off the leading number. When this happens knowing approx. when the airframe was built helps figure out the missing digit. In this case I know the KC135s were all built between FY1955 and FY1964, so it would be fair to say that the missing digit on your aircraft is a "6" or 61-0268. I'd guess it was delivered late in 1961 or early 1962.
This doesn't work all the time. C-130s have been in production so long it can be tougher, knowing if it's an "E" or an "H" model etc can help. Sometimes the tails numbers are contrived and don't follow in any particular sequence.The AF1 747s have contrived serials 82-8000 & 82-9000 to match the previous AF1s 62-6000 & 72-7000 which also had contrived serials. if you take out the leading digit and the "-" they become 26000, 27000, 28000, & 29000 and they all match up nice and pretty for the press.
C-17 tail #s for the most part, but not all, are contrived to match the production number, i.e. the 81st C-17 built has tail # that ends in "81"
Oh, and the 940th ARW is based out of McClellan ANGB in Sacramento.
edit: correct details
[Edited 2004-10-12 19:55:03]
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