Final answer:
The historical significance of the plane crash is that it marked the first fatal crash for Delta Airlines in 95 million passenger miles.
Step-by-step explanation:
The historical significance of the plane crash that occurred at Boston's Logan International Airport on July 31, 1973, is that it marked the first fatal crash for Delta Airlines in 95 million passenger miles. This event is significant because it represents a tragic milestone for Delta Airlines. Prior to this crash, Delta had a strong safety record, but this incident highlighted the risk and potential dangers associated with air travel.