Complex sentence: The cause of the crash is as of yet unknown, and a routine maintenance check of the Airbus A320 aircraft had occurred just a day earlier on March 23 by Lufthansa Technik at Düsseldorf Airport, according to the Germanwings CEO.
Split into simpler sentences: The cause of the crash is as of yet unknown. A routine maintenance check of the Airbus A320 aircraft had occurred just a day earlier on March 23 by Lufthansa Technik at Düsseldorf Airport, according to the Germanwings CEO.