How do hijackers hijack vehicles?
A gun. That is how they used to hi-jack passenger airplanes. Now, airplanes have US Marshals on board AND some flight crew carry weapons, believe it or not.
The 9/11 hijackers hijacked the planes because Osama bin Ladin and the fellow members of al Quada are Muslims. That means that they believe in Allah. (or God) They hijacked planes because they have 24,000 gallons of jet fuel in the plane! They bought little knives that anybody can buy from a hardware store so nobody would think that they would hijack a plane and kill about 4,000 people!
An aircraft hijack is when a person, or group of people, forcibly take control of an aircraft while it is in flight. Hijacking can result in the aircraft being crashed into a building, such as in the September 11 attacks, the hijackers making demands using the passengers as hostages or the aircraft could be being used to travel to a certain place.