11.   National Transportation Safety Board officials have said the evidence they have so far indicates the hub piece onto which the fan blades of the engine were mounted came apart.

12.   Officials also have singled out problems with the engine turbines and fan blades.

13.   Put long plastic bags over the fan blades and secure them with masking tape.

14.   Remove all parts from the fan box and insert rubber bushings into each fan blade.

15.   The devices have poles with looped brushes on the end that are slipped over the fan blades to clean the tops and bottoms of the blades at once.

16.   The penalty followed an investigation by the Federal Aviation Administration into shortcuts Boeing took almost a year ago on inspections of engine fan blades.

17.   Warped fan blades will wobble and wear out the fan bearings.

18.   Vacuum around these, but be careful not to damage or bend the fan blades.

19.   While the fan blades are spinning, each squeeze of the self-refilling bulb delivers small amounts of water into the enclosure of the hood.

20.   With a tape measure or yardstick, measure the distance from the ceiling to the tip of a fan blade.