Did anyone know this story happened in Hong Kong Int'l Airport on December 7, 2003? A piece of thing (I donno what was called) falling off from a boeing 747's left wing after reaching the sky. What exactly is that? What does it effect on the plane? Here is a photo got it in newspaper.

In that photo it looks like part of a slat is missing. Slats have the same purpose as a flap, allowing the plane to remain airborne at a lower indicated air speed without raising the angle of attack. When deployed they give the appearance of the wing leading edge moving forward and tilting downward away from the main wing structure. I am not familiar with Boeing's mechanisms, but on some aircraft slats are propeled by a mechanism resembling a screw jack.I forget which model plane I was on at the time, but I recall hearing the motors that operate either the plane's flaps or slats while the airliner I was riding taxied out for takeoff once. Apparently on that model the motors were located in the main gear wells or anouther compartment under the passenger cabin.