81.   Military officials again Monday refused to speculate about what caused the crash.

82.   Most crashes are caused by a bomb, mechanical failure or pilot error, Pope said.

83.   MSN officials said the crash was caused by a growing number of subscribers who are sending a growing number of messages.

84.   Navy officials say they now believe an engine malfunction caused the crash.

85.   NATO officials initially said engine problems may have caused the crash, but May said the exact cause is not yet known.

86.   Neither the National Transportation Safety Board nor the FBI, however, has ruled that the crash was caused by a criminal act of sabotage.

87.   No evidence in hand yet to indicate what caused the crash.

88.   No one on the ground was hurt and federal investigators are not sure what caused the crash.

89.   Offi cials say a landing gear malfunction caused another crash, and pilot error was blamed for a sixth.

90.   Nolan said there was no immediate indication of what caused the crash, but he noted that all aspects of each flight are monitored in a control center.