Simplify the following text for a Grade 5 native English-speaking person.
Original: On Tuesday , September 11 , 2001 , the aircraft flying this routeâ '' a Boeing 757-222 â '' was hijacked by four al-Qaeda terrorists , and subsequently crashed into a field , as part of the September 11 attacks .
Simplified: It was hijacked by four men as part of the September 11 , 2001 attacks .