A suicie attack is an attack upon a military or civilian target, in which an attacker intends to kill others, knowing that he or she will either certainly or most likely die in the process (see suicide). The means of attack have included vehicles filled with explosives, passenger planes carrying large amounts of fuel, and individuals wearing vests filled with explosives. Synonyms include suicide-homicide bombing, martyrdom operations, predatory martyrdom. Strictly speaking, an attack may not be considered a suicide attack if the attacker is not killed (although they might hope and plan to be), or if there is some question as to whether their intention is to be killed (even if the attack is certain to kill them).