Don't ever make a joke about a bomb on an airplane, if you don't want to risk expulsion. Expulsion is being kicked out of something, like a club, a school, or an airplane.
If a Girl Scout ate all the cookies she'd already sold, she might face expulsion from her Girl Scout troop, and an unruly high school student who threatens to hit a teacher risks expulsion from school. Historically, many religious and minority groups faced expulsion from countries where their beliefs weren't tolerated. In fact, the Latin root word of expulsion is expellere, "to drive out."