During WW2, it literally took a village to run the air war (well illustrated in the poster to the right).  A much forgotten part of WW2 is the many ground crews or groups of mechanics who serviced the B17's and kept them flying.  During all the missions that were flown, the planes were constantly pushed to their limits and shot at.  There weren't a lot of extra planes to take their place, so repairing what was already in use was the only choice. 

 

To the right under the picture is a YouTube link to a video whose purpose was to recruit men (automobile mechanics, machinists, etc.) for this invaluable job. 

As everyone knows, even today, a good mechanic can be hard to find.  Check it out!