 The Civil Aviation Authority's Air Accident Investigation Branch (AAIB) have been informed and are due to begin their investigation , into the crash.
<fluency>  The Civil Aviation Authority's Air Accident Investigation Branch (AAIB) have been informed and are due to begin their investigation , into the crash.
 The Civil Aviation Authority's Air Accident Investigation Branch (AAIB) have been informed and are due to begin their investigation into the crash.