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 and facilities ranging all the way from a filling station to a machine shop. And for all of this overhead one naturally has to pay. The actual cost of plane maintenance depends entirely upon the amount of use made of it, exactly as with an automobile. I don't believe any reliable estimates of up-keep are available.

The number of hours a motor can run, without overhauling, depends not only on the motor itself but the character of the attention given it. Meticulous care of a plane's power plant is vital. It is not that the motors themselves are any more complicated than the engines of large automobiles, but there simply aren't any service stations 10,000 feet in the air. An oversight on a highway means only inconvenience; one aloft means inconvenience, too—the inconvenience of coming down where there may be a landing field or there may not.

All of which information may sound indefinite. But I believe exactly the same uncer-