1.   As they began their latest excursion, the cosmonauts reported a white powdery substance around their outer airlock hatch.

2.   A loose screw in a Columbia airlock hatch jammed the latching mechanism, preventing two astronauts from opening the door for high-priority spacewalks.

3.   Engineers began testing the airlock hatch late Monday.

4.   However, planned spacewalks by astronauts Tammy Jernigan and Tom Jones were thwarted by a jammed airlock hatch.

5.   However, prior to giving final clearance, U.S. managers want to clear up some lingering concerns about a balky airlock hatch aboard Mir.

6.   The screw belonged in a braking component within a gear hub that was fastened to the airlock hatch.

7.   But the walk was called off when the airlock outer hatch failed to budge.