Porter is in the news for bumping several passengers, including a UM, to reduce weight. It's been reported that they were rebooking them for the next day. The thing that strikes me is that they should have been providing hotel accommodation in that situation and they would need to check that the passengers are old enough to be able to check in to a hotel. With some hotels, even 18 might not be sufficient, so it's not even purely a UM issue. (Though definitely the 14-year-old has no chance.)

Parents outraged after girl, 14, forced off Porter Airlines flight