Well, perhaps. Here's the story... First, this whole thing begins with the fact that the Space Shuttle boosters were manufactured in Utah, and had to be transported, by rail, to Florida. That meant that such factors as tunnel bores and bridge width determined the size of those boosters. (One of the first rules of railroading is to never try to increase the size of a tunnel bore by trying to force an object larger than the bore through it.) Further, NASA has its own private railroad. When the boosters return to Earth and are tugged to shore, they are loaded onto railcars and shipped via rail to the processing building for the next mission. Make sense so far? Okay, but then the fun begins, for you see, we now tack on the story of why the rails of the track are 4 feet, 8 1/2 inches apart, a dimension that also determined the tunnels and bridges: U.S. Railroads were originally built by British expatriots, and adopted that gauge because that's the gauge they used in England. The English used that gauge because that was the width of the track for the tramways that preceeded them. The tramways used that gauge because the wheels and axles were made on the same jigs as the axles for horse drawn wagons. That width was used because the wheels on the wagons had to match the ruts in the roads. Those rutted roads were originally built by the ancient Romans. Those roads were made only wide enough to accomodate the width of a chariot, the wheels of which made those original ruts. So, there's the story. Only some of it is probably true because the legend ignores the fact that early railroads in both Great Britain and the U.S. experimented with more than one track gauge. Yet, both countries did settle on 4' 8.5", which is a very close match to those rutted roads.

Snopes.com has a fairly thorough writeup, which concludes that: "This is one of those items that -- although wrong in many of its details — isn't exactly false in an overall sense and is perhaps more fairly labelled as "True, but for trivial and unremarkable reasons."" They show that the connection is less direct and more coincidental than the humorous email story suggests. The entire article can be found here: http://www.snopes.com/history/american/gauge.htm

Well, that makes a nice story and could be demonstrated potentially true - back to front, so to speak. However, aircraft and spacecraft components are just as easily and just as frequently shipped by air. Large components are often shipped by 'Guppy' aircraft, equipped with enormous, oversized cargo bays. The following links show the Aerospatiale A300-600ST Beluga Super Transporter, built to transport large aircraft components between factories: - http://www.airliners.net/info/stats.main?id=19 - http://www.aerospace-technology.com/projects/stbeluga/ One of the pictures on the latter site shows a Super Transporter being loaded with a fuel tank for a spacecraft. NASA actually owns its own Super Guppy, shown at: - http://jsc-aircraft-ops.jsc.nasa.gov/guppy/ Or try the "All About Guppies" website at: - http://www.allaboutguppys.com/