I'm sure the next time the terrorists execute one of these hijackings, they will be flying on round-trip tickets.
The Sept 11 hijackers travelled on return tickets. Which they brought with credit cards, and not with cash.
a) Suicide bombers don't care if they buy return tickets they're not likely to use.
b) I understand that half the hijackers didn't actually know it was a suicide mission. Though I'm not sure how anyone can know this for a fact, of course.