Is there a clear contradiction between 'The duty officer replied that security personnel at headquarters had just begun discussing the apparent hijack on a conference call with the New England regional office.' and 'There have been dozens of plane hijackings before 9/11.'
The duty officer replied that security personnel at headquarters had just begun discussing the apparent hijack on a conference call with the New England regional office.###There have been dozens of plane hijackings before 9/11.