Complex sentence: His meeting was scheduled to take place on an upper floor of the building, but he was delayed in the lobby before boarding the elevator, and was able to leave the World Trade Center safely after the first plane hit the building.
Split into simpler sentences: His meeting was scheduled to take place on an upper floor of the building but he was delayed in the lobby before boarding the elevator. He was able to leave the World Trade Center safely after the first plane hit the building.