Complex sentence: During the terrorist attacks of September 11,2001, the Flaggs and their friend, Barbara G. Edwards, were on board Flight 77, heading to a family gathering in California.and died when it crashed into the Pentagon, they were on board.
Split into simpler sentences: During the terrorist attacks of September 11,2001, the Flaggs and their friend, Barbara G. Edwards, were on board Flight 77, heading to a family gathering in California. They died when it crashed into the Pentagon, they were on board.