Complex sentence: On September 10, more trading in Chicago saw the purchase of 4,516 put options in American Airlines, the other airline involved in the hijackings, with a mere 748 call options in American purchased that day.
Split into simpler sentences: On September 10, more trading in Chicago saw the purchase of 4,516 put options in American Airlines, the other airline involved in the hijackings. This compares with a mere 748 call options in American purchased that day.