Some, famous as “voluntary†customers, take a understanding with an airline and give adult their chair in lapse for moody vouchers or cash. But others, famous as “involuntary†customers, are simply kicked off a plane.
Article source: http://www.huffingtonpost.com/entry/airline-overbooking-policies_us_58ed14a0e4b0ca64d919d3ab?section=us_travel