1.   At first, engineers believed some contamination in the valve was keeping the device from opening and closing properly.

2.   Boeing engineers believe such a series of events would never occur during flight.

3.   A NASA spokesman said engineers believe a temperature-regulating valve in the cell was at fault.

4.   But many auto engineers believe that the hybrid approach represents a reasonable compromise.

5.   Computer engineers once believed that only sophisticated artificial intelligence software could accurately simulate a person.

6.   Dane said that aerospace engineers generally believed the sonic-boom noise problem was ready to be solved.

7.   Engineers believe the hull of the module was breached below the base of the panel.

8.   Engineers believe the rubble is the only thing keeping the foundation from caving in.

9.   Engineers believe it is possible the aluminum cover plate was improperly installed before the flight and rattled free because of the vibration of the igniting rocket engines.

10.   Engineers believe the breach may be hidden beneath the base of the mast.