Complex sentence: In 1996, Hani Hanjour who would later fly a hijacked airliner into the Pentagon was admitted to the Sierra Academy of Aeronautics, but before beginning flight training, the academy arranged for Hanjour to take intensive English courses at ELS Language Center in Oakland.
Split into simpler sentences: In 1996, Hani Hanjour who later flew a hijacked airliner into the Pentagon was admitted to the Sierra Academy of Aeronautics. Before beginning flight training, the academy arranged for Hanjour to take intensive English courses at ELS Language Center in Oakland.