Tugboats were not escorting the massive cargo ship Dali when it lost power in the Port of Baltimore and slammed into the Francis Scott Key Bridge, toppling the span and killing six people. Maritime experts told The Associated Press that this week's disaster is drawing renewed attention to whether such tugboat escorts should be required in the nation's ports to nudge increasingly big ships to safety and protect bridges and other critical infrastructure. Cost-conscious shipping companies have over the years resisted calls for extended tugboat escorts that can add tens of thousands of dollars to every transit.