Whether you're flying from New York or New Orleans, Lisbon or London, airlines continue overbooking to compensate for “no-shows” all the time. Simply put, they sell more tickets than they have available seats. And it's not an illegal practice. But the US Department of Transportation (DOT) has rules to protect you.
Is it common for airlines to overbook flights?
The point of all this is to ensure that the plane is full when it takes off, because empty seats are a financial burden for airlines. According to some travel experts on overbooking flights statistics for every 100 seats available, about 150 tickets are sold. So most flights are undoubtedly overbooked.