Based on the last time I was in the Everett factory (3 years ago), Boeing requires all machinists have foam cutouts in their toolboxes and that every tool is re

Based on the last time I was in the Everett factory (3 years ago), Boeing requires all machinists have foam cutouts in their toolboxes and that every tool is returned to the toolbox at the end of the shift. Tools checked out from the tool crib must also be returned to the tool crib at the end of the shift. This has in practice greatly lowered the amount of lost tools in aircraft, since every tool is accounted for. I imagine that the FOD in the fuel tanks is most likely lots of scrap from drilling out the holes rivets are placed in, and probably some rivet debris as well. There most likely is a process for clearing that out from where its generated (rivet holes are not often pre-drilled), and there may be inadequate supervision of the machinists doing that.